Okay guys I've had this problem for awhile and I think I know what is causing it but I'm not real sure. My sixer has been running rich just on the driver's side, bank 2 sensor 1 has been setting codes since I bought the car. I replaced the o2 upstream sensor three times and it never went away. Well two weeks ago I replaced my clutch and when I took the exhaust off and I noticed that there was no screen on the front cat. So I put a pry bar down the cat and found out that it had been gutted. I'm not sure if the secondary cat behind bank 2 sensor 2 has been gutted too cause I couldn't get my bar down that far. Here's my question, could that be the reason only that side is running rich and if so since I can't afford to get new cats would o2 sensor spacer solve my rich problem?