94 s-10 pickup 4.3 v-6 vortec

This truck as 177000 miles on it.. I bought it from a guy my brother works with, I just had air temp sensor , fuel filter, and exhust gasget from manifold to pipe all replaced. The problem I'm having has always been ther... when accelorating it hezitates and wants to stall, now the fuel pump was tested and pass as OK, this truck has a K&N air cleaner kit on it. I'm at wits end trying to figure out what the problem could be. Im thinking throttle sensors or maybe timing or something along those lines. Any advice would be great.