Running rich on one side.
 

Hello, little info on the car. I just bought my 02 GT about 2 weeks ago. It has an after market exhaust, under drive pulleys, CAI, and 3.55 gears along with a diablo tuner with pre-set tunes. The car started running rich soon after I got it. I had it at a shop where they put it on the dyno and told me I was running at about 25 percent on my long term fuel. He said it was probably my 02 sensors going bad. So I've replaced my front sensors today as well as have new plugs. I took it for a drive with the tuner plugged in giving me readings. I'm now running 10 percent on one side and 25 percent on the other. Where should I turn now on this issue? Any help would be greatly appreciated.

Exhaust leak on that one side just before 02 sensor. Intake leak on that one bank sucking un metered air.

Well after taking it to 3 shops, replacing injectors, doing a compression check, I found the exhaust leak myself when 3 shops couldn't. I had it fixed today and finally seems to be running correctly.