@ fraser yeah i have changed my tune a little on the bad gas theory after pulling the codes, but just to keep my mind from wondering and i think its a logical thing to I'm still going to pull a sample from the fuel line. I've already purchased some iridium NGK plugs. I'm going to play with swapping the coils around to see if i still get misfires. i hate not being able to devote more time with my work and all but i am going to do this first before getting some professional help.
Brutal i still have your number and might have a side project for you if you have time if nothing changes

I think professional assistance is really necessary to sort this problem out, but you can, of course, check the on-plug coils if you have the kit.

Is it possible to sort out the pump question - if one tank feeds one bank you have the possibility of water in one tank.
I can't understand otherwise why all 4 cylinders would die.

I'd like to figure out the flow schematic as well. I have taken a look @ graphics, but they dont lead me to any conclusions. Might have to pop my hood.

From what I can see, the Supercharged version has the same single fuel feed as the NA version, but the transfer pump on the drivers side of the NA model is replaced with a fuel pump. They both still feed the same supply line to the engine though. I don't see separate fuel feeds from both pumps to the engine. I am only looking at the picture though. There is no info on this in Alldata that I can find. The actual point I meant to make though is that the only way to drain all the fuel from the tank is to remove both pump modules and suck the fuel out from the openings! Tough job to drain the tank.

@ oldmots. Where did you see a single feed in Alldata? I looked pretty hard. I was hoping it was a split rail configuration and that alone would drive a few more conclusion as to why the # 2 bank is dropping out. With a single feed and no drop in pressure across the fule manifold without it running leads us right back to the route the OP is taking, ignition troubleshooting.

My worst fear would be an ECM or a skipped tooth on sprocket.

@ oldmots Never mind I see that you didn't find the same thing I was looking for! (Did that make sense?)

I don't pretend to be an expert at all but how would you take out an entire bank with an ignition fault ?
Each injector and plug is individually driven by the ECM - I can't see any electrical fault that would do that.

I didn't give that much thought when I typed that idea, but I do think you have a valid point. Hmmmm

Without actually seeing & hearing the noise it's impossible to say...but i'm thinking kind of the same, misfires are caused by timing problems or ignition problems.

How could it be a fuel problem? There was obviously enough fuel to heat the whole exhaust & melt the rear fender liner, so i'd be very doubtful of fuel being the problem.

A misfire on one cylinder you could put down to a bad plug, bad coil or bad wiring somewhere between the ECU, coil & plug.

A whole bank is something much bigger, what would cause the spark to fire at the wrong time on a whole bank? Not much, so i'm leaning towards the camshaft timing / slipped a tooth on the sprocket theory... This might explain the "clatter" every cylinder on the bank firing at the "wrong time" because the valves aren't in the correct position when it fires.

BTW i'm no expert either! If i was in your shoes i'd get the car on a truck over to Brutal's shop, don't start it anymore, if the worst is true then the next crank could see valves vs. pistons...

Yes, makes sense, the only common thing to a bank is the timing chain.
The OP could easily look to see if the cam flats are lined up couldn't he ?

without looking at the wiring diag if I remember the injectors and coils on each bank share common points for power. also pinch a wire harness say to the injectors like the trigger and the injectors go full tilt for that bank or coils dont fire. but if coils dont fire youre not gonna have a cat fire since nothings burning. not jump timing from chains and that can defintly do it since youre now firing the mix and opening the exhaust valves too early letting the fuel mix continue to burn in the exhaust manifold and cat

Brutal, I defer to your greater experience, but if the other bank is running OK it will be keeping the catalysts very hot, so unburnt fuel from the defective bank could ignite there. Or am I wrong ?

My thinking on this is that the cam tensioner has let go on the misfiring bank and the cam has changed timing, chain clattering and allowing unburned fuel to burn in the catalysts and overheat the exhaust on that side. Not may things can affect the entire bank but the cam timing.

The pictures of the SC tank and the NA tank are found in Alldata here:
Powertrain Management>Fuel Delivery and Air Induction>Fuel Tank>Description and Operation

Keep in mind that fuel can be contaminated with many things. In the case of my wife's Volvo, it was not water but something else. Who knows what that could do to cats and injectors. They had to replace all of her injectors and the fuel pump.

OK, if it is a camchain slip, then a compression test should reveal it. Values should be very different between the two cylinder banks

There are NOT 2 fuel pumps on either car NA or SC. the fuel pump and common feed line that goes into the drivers side fuel rail US, and feeds a crossover pipe to the other side. The only way you could have 1 side affected with fuel is IF crap pumped into the drivers side rail and only enough to cause issue for those 4 injectors and the other side received NO contaminants. It would also NOT be common for the chain/tensioners to fail on this engine.Not impossible, but not likely on the 4.2. damn you guys are gonna make me diagnose this arent you?????

also if the cat failed. melted, and is therefor clogged your not gonna be running on that bank and will defintly be misfiring. Im trying to remember if the injectors are bank fired per bank. they all have seperate neg drivers from the ecu but many injector system are may not be sequential, but pulsed in batches. Not till you do direct injection is it that neccessary to acuratly time the injector. I just dont remember on that one. Also the fact that you have a code for cat failure and its glowing. if it runs poorll all the time pull the cat down from the manifold and run the car. It will substitute values for AFR's with open exhaust. We run them all the time with cats off the car when replacing a engine on initial startups and warm up. if it runs fine with cats unbolted, "Thars yer sign"

Yeah I found that tidbit. As matter fact I had it posted till alldata started surfing my pics. Seems they dont like a direct link. LOL I thought you might have had a found a split fuel rail configuration, but I guess thats not possible.

I know you shouldn't believe everything you read and I bow to your superior knowledge but the X350 Training Manual does say there are two fuel pumps on the XJR. There are two shown in the Electrical Guide as well.

"On supercharged vehicles there are twin fuel pumps located in the fuel tank. The additional pump receives its power via a fuel pump delivery module located in the luggage compartment near the REM."

and

"A variable speed fuel pump module is located in the RH compartment (a second pump is located in the left hand compartment on supercharged vehicles)."