1994 Chevrolet K2500 extended cab 4wheel drive 5.7 V8 automatic

There may be a vacuum leak, snug up the intake manifold bolts, and check the TBI base gasket. May also be a fuel pressure issue, fuel pressure should be 9 to 13 lbs.

What's a TBI ?

The TBI is Throttle Body Injection. It is what delivers the fuel into the engine. It has 2 fuel injectors on top of it over the throat of the air intake along with the fuel regulator in it. That gasket under it should be checked and the TBI should be cleaned up.

I cleaned the TBI. I'll check gasket . To me it sounds like it's loading up?

Ok, take the air cleaner off, start the engine and watch the fuel mist come out of the 2 fuel injectors. It should be a niece cone shape mist coming out, with no droplets of fuel dripping from the injectors. If it is not a nice cone mist of fuel, then the injectors are dirty internally. You would want to run some fuel injection cleaner threw the gas. It would take some time for them to clean themselves out, like a tank of gas.