Chevrolet Repair: MisFiring, port fuel injection, power brake booster

Question
Thanks For Your Time, I Have a 95 Blazer S-10, 4.3 Vortec, At Idle and normal driving, It Seems To Misfire, Sputter, and when power is needed like up hills, trailers, etc, it dogs for power, Ive replaced distributar, cap, wires, plugs, exaust from cat back, trans is fine, could it be the multi port fuel injection system?, if so, is it easy to replace?, ive been trying to figure this out for about a year now and i need some help, thnaks for your time and any help would be much appreciated., Bruce

Answer
Hi Bruce,
I doubt the fuel injection is the problem, but a fuel pressure test would be a good idea.
Fuel filter comes to mind.
If you have had an actual miss for over a year, you may have melted the inside of the cat converter.
Vacuum leakc can cause low power and a miss.
Some sources of leaks are hoses, power brake booster, EGR valve sticking, PCV valve, transmission modulator valve if it has one, and other vacuum operated accessories like a/c controls(yours may be electric).
Burnt valves, or a broken valve spring are other possibilities.

Van