Throttle body

I'm have a 1990 Chevy G20 van w/a 5.7 ltr engine. The throttle body acts as if it were choking for air. It backfires through the T.B.I. It blows black smoke, the van dies a lot, but at times it runs w/o any problems. When the engine is cold it runs o.K, but as soon as it get hot, it****** and sputters and the T.B.I. Will backfire at times. I was told it was a bad F.P.R, or a clogged fuel filter, or some sensor. And I don't have any vacuum lines directly attached to the f.P.R. Money is very tight for me, is there anyway to help me solve my problem as cheaply as possible? Please send your answer to ap2151@yahoo. Com. Thanx!