Help with Stalling problem

My friend owns a 99 Chevy s10 Blazer it's a 4.3L V6 4WD

We are having problems diagnosing the problem

The engine rotates but does not start or when it does start it stalls as soon as you accelerate.

We have changed the fuel filter, the pcv valve, checked the distributor, cleaned a few sensors, so far no luck...

There are no warning lights on, and we have went through the entire trouble shooting manual...

Any suggestions/help is greatly appriciated

Sounds like air/fuel restriction to me. Did you check the fuel pressure?