Chevrolet: 1985 2.8L V-6, backfires, no idle, throttle position sensor, air control valve

Question
hi, i recently put a 2.8l fuel injected v-6 into an 85 firebird(motor came from an 85 camaro) block has about 97k on it, but was rebuilt at 80k. during the swap, i replaced the timing chain/gears, coil, distributor module, plugs, wires, cap, rotor, and of course all the fluids, filters, etc. i also replced the stock distributor with one from an 86 2.8 due to damage to the old one. i also performed a compression check prior to removing the motor from the camaro, all cylinders were over 125lbs, with the highest at 165. i don't have a timing light, but ive never had this much trouble with backfiring before. no matter what i do with the timing, the car will not stop backfiring. starts easily, it was idling nice, but now it wont idle at all once warmed up. also, it doesnt backfire for the first 4-5 minutes after its started cold. also, driving down the road it "chugs" if you try to accelerate lightly or maintain speed. under hard acceleration, its a beast! absolutely no backfires, chugs, or misses at wide open throttle. and no backfires at idle either. (when it would idle). i have cleaned and checked the length on the idle air control valve, checked and set the throttle position sensor voltage, and replaced the exhaust with all 2.5" pipes, 80 series crossflow flowmaster muffler, and dual tailpipes. it did help with the backfiring, but still does it. also, the cat converter has been removed. help me, i've been doin this for 16 years and i dont know what to attack next. i know i could fix it if i just kept throwin parts at it, but i dont have that kind of $

Answer
PETE,
    OK - I bet  that there is something wrong with the distributor  or timeing  and or plug wires so I would not put any more money  into  it , just check to see if the dist is in right -and than the timeing -and the plug wires - etc. if a dist  is off by only one tooth it will cause all kinds of head achs. so check the dist to see if it is on no# 1 plug  . and first off re-check all of your plug wires.
and look at the dist. cap - for any shorts or cracks. I bet it is a small thing that is doing it. as long as the cam was put in right.and timeing gears  or if it was running in the past , it should be ok. ok