OK, got an annoying issue with fuel trims- HELP :)

[kwiktsi]

OK, been tuning this thing (twin turbo LS2 GTO) for several days now and it has been driving me nuts. I finally just said screw it and am running it maf only and it is virtually flawless (thanks 5 liter!)- BUT it is still doing something it has done since when I was doing my VE tuning. I will get it all dialed in with -2 to 2% errors max, runs and drives perfectly, I have the LTFT's disabled, but the STFT's will be perfect almost all day, then it will slowly start adding up to 16% or so at idle the more I drive. IAT's are good, coolant is consistent, etc., it just starts needing more fuel at idle out of nowhere. The car will also start to idle just a touch on the rough side like it is too lean when this happens too. Everywhere else looks to be pretty decent still, but the idle is going lean. I was thinking it was IAT or ECT related, but they were consistent throughout the day.

Is there anything else I should be looking for in the tune that could lean it at idle after driving it a while?
Joe

[kwiktsi]

Actually, just looking at my logs, and it appears that even my WOT fueling is leaner too, so apparently, the car just gets leaner and leaner as the day goes on. I could see if my IAT's were going higher, or my ECT was off, but is all consistent from log to log.