badnissan720

Hello I have a 86 nissan 720 with the z24i eleto-injection motor. I bought it last dec had blown head gasket. Got it took apart and cylinders had bad marks, so I decided to rebuild. Got bord 40 over head redone hole nine yards. Finely got it all back together got timing set idled good so drove it around my sisters neighborhood few times, then next weekend had tag for it so drove it home witch is about 27 miles did good. The next day was gonna drive it to store and it made it about five miles down the road and started missing so turned around and went home. Figured out it was overloading gas, called around and was told it was probably ignition module. Went to buy new ones and found out it had modules and coils off a nissan sentra if I'm remembering right. So bought new modules and coils for the truck and put them on drove truck ran fine the next day went to drive it again and stated overloading again went back home let it sit there and run i smiled sometthing burning shut truck off and figured out the module for the exhaust side was fried. Thought just got bad one from part store so returned it got another one and put it on didn't last ten min and it fried. Does anyone know what would cause this?