stumblin' off the line

my 97 gmc sierra w/ 350 has an issue with falling on it's but off the line . if you idle her up against the converter she leave fine otherwise no dice . she's stock save for throttle body spacer , duals with glass packs, programmer ,and home made cold air kit . she was doing this prior to any of the add ons . it's got 217 and some change on it now. any ideas im at a loss .

Scan and look for o2 sensor activity, tps activity, maf been cleaned?

maf cleared no codes ill check on the o2's even replaced the regulator . who knows if it was a carb i'd have figured it out by now

I had the same problem I had to put in a chip programmed for dual exhaust. I was told that with the reduced back pressure, it put the computer in limp mode all the time. I put in a performance chip in the computer and it was new truck !

The truck had duals back to the muffler that then came out in a single three inch tip after can't see the muffllers and tail pipes making that big of a difference plus it has a program in it that allowed me to make the adjustments to it for aftermarket exhaust .