i just bought a 83 zxt to swap into my 240z, but i want to get it running good before i do the swap. I just bought the car, so i don't know much about the past work done on it and problems with the car. The owner actually said the car ran perfectly fine one week ago, and only started doing this after a potential buyer went to look at the car while he was gone and was able to pop the hood and look around since the car wasn't locked. The car starts and runs smooth and good at idle, but when the car is cold, it'll backfire sputter when revved. before it warms up, the rpms won't go past 1500rpm or so without heavy backfire and misfire. if i let the car idle for 10 mins and let it warm up a bit, it'll rev to 3000rpm before backfiring and missing. boost hit a max of 1-2 psi. I'm leaning towards fuel related problem. where should i start? Thanks.