missing and backfire out tailpipe

My truck has a miss and backfires out the tailpipes. It idles fine and sound fine when reving or holding it reved up, but it misses and backfires under normal acceleration until I drive for 15 to 20 miles then it runs fine.
The truck is a 92 chevy withTBI. It has a 383 stroker, custom chip, it has new accel rotor/distributar cap and wires, splitfire plugs, msd coil,and holley ingnitoin module. I had a holley 670 TBI on but put stock TBI back on but didn't help also tried replacing all the new ignition parts with my old ones thinking maybe one of the new ones was bad. The only other thing I can think of are the main computer or the spark module. Any ideas?????

I had a simliar problem with a '73 K10 carb. 5.7 but mine would idle fine but any throttle applied and it would miss and backfire it turned out that the distuributor hold down bolt had loosened up and when the gas was pressed the dist. would turn taking it out of time. some where you have a problem with your timing being thrown out of whack.but its strange that it will be fine after 15-20 miles. After you drive it and it straightens out if you shut it off does the problem start again? and when you are driving it does it misfire and or backfire only during acceleration or while you are holding speed on the road?

I still havn't fixed problem, any ideas?? Since my original post I have also replaced fuel pump, spark module, MAP sensor, pick-up coil, solinoid for egr, temperature sensor, converted my 1 wire O2 sensor to 3 wire, I've had timing set to 0 degrees as well as everywhere else, also tried adjusting the throttle position sensor, I tried unpluggnig my knock sensor as well thinking it might be retarding the timing.I can't seem to find any vaccum leaks either. The only things I can think of is possibly the computer is bad also heard possibly an intake gasket leaking on the inside of motor. Again, idles fine, revs fine,runs fine after around 2500 RPM but misses and backfires under normal driving until I drive several miles sometimes it takes 15-20 miles then it runs fine.

I recently had the exact same problem with mine. Turns out that it didn't like the aftermarket coil. Don't know why, but I put on an original coil and it ran fine. Scab a used coil from another motor or get a new one ($50), but I'm positive that is your problem.

Still no luck. I have tried the stock coil, stock TBI unit, and another rotor/distributer cap. It acts like it the computer is either retarding the timing or not advancing it like it should. Any other ideas??

have you tried hooking a vacuum gauge up to manifold vacuum yet to see if you have a normal vacuum reading. Vacuum gauges can should internal engine problems as well, that is what I would try. or maybe try a compression test, there could be an exhaust valve not fully closing or something like that

My boss had a 95 chevy with a 350 tbi, he rebuilt the motor, put different heads and cam in it, and could never make it run right. He spent hours and hours on the phone with his chip people, trying to make it run right on the bottom end. It would scream after it got above 2k, but anything underneath, it was a dog. Turns out the computer wasn't able to compensate enough for the camshaft and the bottom end was never there. He ended up putting a rv cam in it, and it ran fine ever since. His theory on the deal was that if GM could have put a bigger cam in it and made more power, they would have, but they couldn't make the computer run the motor correctly.