I was stopped at a light today when my truck started shaking and the idle was really rough and choppy, i threw it in neutral and held the gas at about 1000rpms, that stopped it, but worried the heck out of me. I was really watching it after that (did what had toand went home) it didnt do anything like that again. My oil pressure gauge seems to fluctuate a little more, but nothing else is wrong. Still runs about 28psi at low idle. its a 91 chevy w/ tbi 350. Anyone ever heard of this or know what it might be?