I need a little direction. 1998 GMC 2500 4.3L 117K miles. MIL illuminated P0171/P0174-no drivability complaint. LT trims at idle climb to 160 on both banks. Trims hover around 140 at 2000 in park. I did not look at trims at WOT but did graph pre-cat O2s. Both ... Login to read more.