Work is a little slow right now so I have more time than money. I'd love to throw on a lower pulley but at 150k I'm not trying to push my luck and pop a head gasket or something..and the whole money thing lol. I want more sound and a bit of performance wouldn't hurt. Aside from dealing with a cel what would it run like using the factory cats with no innards? I'm sure running a strait 2.25" or 2.5 pipe would be better but would take a good amount of quality fab work.

 

I have these on my XJR at the moment....... No CEL not a massive sound change, I cant even tell you if they offer more power either, I fitted them as the cats had rusted badly and I took them off my track XK as a temp fix...

 

You can use standoff "simulator" bungs on the downstream O2s to avoid the CEL. They basically just move the sensor probe of the downstream O2s further out of the exhaust stream, simulating the restriction and flow changes of the cats. You basically just need to buy tall, fully threaded bungs, run the car and check for CEL, cut a bit more off the bung, check for CEL, cut a bit, and repeat until it reliably doesn't throw a code. It's a decent bit of work, but not at all hard. And while data is limited, it sounds like catless downpipes are worth maybe 5-20 hp and a couple pounds of weight reduction.