Hi, I have owned a 2004 XJR for almost a year now. I had the well known air suspension issue soon after buying it (I had researched and expected it to happen) and replaced it with the spring shocks. Other then that, all has been good until a few days ago.

Before I continue, I am in my early 30's but this is my first car, I lived in New York City my whole life until 2 years ago, ( no need for a car there) when I moved to GA (not by choice, army stuck me here) Thus I needed a car. I wanted a big good looking powerful sedan with decent reliability and after much research settled on the XJR. I have read a lot, and tried to figure a lot out myself but I still don't know the name or function of every single engine part so bear with me.

I was pulling out onto a main road and had to pull in fast, one of the many things I love having a fast car for. The engine stalled and I got an error light with restricted performance. I got home, and the next day brought it to AutoZone to check the warning codes. I got P0171 (X2) P0174 (X2) and P1111. It said lean bank something or other and meant restricted air flow, or there is an air leak, or something to do with the engine getting air. I checked the filter and it looked clean to me. The guy at AutoZone said it might be the part on the tube behind the air filter. I can't remember the name but the replacement cost $133. (possibly MAF Sensor?) I couln't go to a mechanic because of course the damn thing broke on Saturday and everyone is closed Sunday. It drives fine slowly but can't go above 3000 rpm so no high acceleration till its fixed.

Anyway, on to my question. I had already been thinking about upgrades to the car. I know XJR upgrades are few and far in between but since I need to fix the air flow anyway, how about this: Jaguar XJ & XJR Direct Air Intake Kit 42L 04-2009 - Mina Gallery Inc they claim it adds about 12 HP, is the $135 worth it over the $49 air filter on EuroToys.com? Any suggestions to upgrade the air intake rather then just replacing with the same stock part? Also, is the $135 Direct Air Intake just a filter or does it replace the part behind it I mentioned earlier in the post (If none of you experts can name the part I'm talking about I'll get the name on Monday)

Would I be able to replace these parts myself with basic instructions or do I need a mechanic with a computer to reset the fault codes to get full power back after I get the parts replaced?

If you have a split in the plastic intake piping, then now would be a good time to replace it with a metal tube.

As a performance upgrade these do bring you an added benefit, typically around 10hp at the wheels https://www.jaguarforums.com/forum/x...ailable-83959/

Also check if the solenoid-powered flap in the airbox is working, easiest thing is just to remove the flap & see if you notice any difference in throttle response.

You need to do a smoke test to find any possible vacumn leaks. If not, check the egr valve. Most likely its one of these two.