Sluggish Acceleration

[speeddemon]

Hi everyone, I am new here. I just bought a 1998 gmc sierra 2500 ext cab 4x4. It has a 5.7 liter, so I was told! I can't see any markings that say it is a 350/5.7. Is there any way to tell that it is indeed a 350? However, the most important question I want to ask is if this truck dont accelerate very good, is that a sign that the tranny may be on the way out? It has 266,000kms and it's original engine and tranny. The guy I bought it from had it for 8 years and said neither tranny or engine had been rebuilt. The fuel pump is whining real loud and the truck will stall after driving for 20-25 minutes, but starts up again right away. The engine sounds real strong. I really dont know where to begin, and I dont want to sink a pile of cash unnecessarily and not cure the problem. I was kinda hoping someone could point me in the right direction.

[txab]

Since you don't know what has been done to it maintenance-wise, you might change the fuel filter, plugs, wires, distributor cap and rotor. Also check your fuel pump pressure. A loud whining fuel pump usually isn't a good sign. Change the fuel filter first and see what happens