02 Camaro lean under WOT

[Bottesini]

Need some help brainstorming an issue. The car had a P0357 (#7 bad coil) code. Ended up changing the plugs and finding the PCM connection was loose. The car ran great sat for a few days and then I drove it again with no problem. After sitting at work for the day the car started up and began having lean issues. On a cold start the idle is very lean and eventually once the car heats up returns to normal. It currently runs fine for cruising and holds around 14.7 afr. However, it hesitates at WOT and runs around 16 + afr. No codes are being thrown and I have checked the fuel pressure and it holds steady at around 60-65 psi at idle and under load. I have not found any vacuum leaks and the idle does hold normal. I have also changed the fuel filter with no luck. Any ideas?

[sjgreen6]

Since you have checked the fuel pressure and changed the filter, have you ever had the fuel injectors serviced? Could be some are gummed up and not letting the fuel through at a high enough rate to keep up with your requirements at WOT. Are you running the original size injectors and have they kept up with all modifications you have made to the engine? Long shot but are you still running the original O2 sensors? Could one or more not be reporting accurately to the computer? Since you are able to check your air fuel ratio you obviously have a wide band O2 sensor and gauge installed. Do you have it on just one side of the exhaust or separate sensors and gauges on each side? If only on one side, then that at least tells you that it is lean on that bank and the other side may or may not be lean.

[0rion]

Sounds like an open loop problem prior to the O2's making adjustments. I'd want to see what the fuel trims look like but bet they're showing lean. My first guess would be unmetered air which could be a vacuum leak. Check pcv hose going to throttle body for a crack on the back side of the 90 where it turns to go to throttle body. I know you looked for leaks but I would go over it with a fine tooth comb. Sometimes those leaks like to hide. That crack in the back of that 90 wouldn't just jump out at you.
Another thing I'd look at is cleaning the MAF. It controls fueling in open loop so never a bad idea to clean it.