Burning Up Distributor Modules In My 1992 Isuzu P/u 3.1 Liter... Why???

[SMOOTHBONE]

here's the skinny:

had engine rebuilt 10k miles ago and still can't get it to run like it did before i had it rebuilt.

symtoms: runs great until it "warms up" then it starts slightly loping or missing a little. my gas mileage goes to pot! then even if the engine is warm and i turn the key off and cycle the power on the e.c.m. the engine will run great again until the e.c.m. is told that the engine is warmed. what is strange is that i have burned up 3 distributor ignition modules in the distributor. I SHOULD HAVE KEPT MY ORIGINAL DISTRIUBUTOR. !!!!! the aftermarket/ rebuilts suck! i did however put an o.e. ac delco module in it and it has lasted the longest... 8 month now... keeping my fingers crossed.

i've replaced all the obvious stuff to no avail. HELP!!!!!! IT'S DRIVING ME NUTS! THANKS!!!