I should have added the truck responds to what the wideband is showing. It pegs like deceleration fuel cut off only im pressing the throttle and it almost dies when it shows lean. When i give it a blip the rpms come back up. its also idling around 14-16 afr when before it would be around 13-14.

the vehicle is a 91 s10 with a 350 in it. the wiring is the same as factory except i made a adapter harness for a 7427 ECM. its been running great until last night. Iv tried googleing the issue but egr always comes up as the issue and im running no emissions with a simple eddy intake for the vortec heads.

after i get it back together ill try to get a datalog to see if that helps.