I have been chasing down an issue with a very lean idle. I did boost leak check the car and found a very bad leak at the MAP sensor bung on my ls6 intake. After repairing and rechecking with air pressure and finding no more leaks I started the car and its is running +20 short term fuel trim and rough. Wide band at +19 afr. When coming out of open loop the car stabilizes to 14-4- 14.9 but STFT are in the +20 area.
When I disconnect the IAT sensor the idle is beautiful but a little rich as it should be showing 13.2- 13.6 on LC1 wideband. When coming out of open loop it stays near perfect stoich but trims are - 7 to - 11 so a bit rich.
I changed the IAT sensor , made sure it was reading within 10 degrees of ambient but the car still will run lean when IAT plugged in and rich without.
I am running speed density and methanol so I really need that IAT and do not know what I should be troubleshooting at this point.
Any help would be greatly appreciated.