Alittle Fuel/Performance Problem...Help?

[KYCOL]

Greetings!

I have a 1994 Chev-S-10 Blazer Vortec 4.3 with a fuel problem...

Recently, I put a new fuel filter, fuel pump, and strainer in it, but I still have a problem.

At lower speeds 48-65 mph the Blazer feels like its straining or loping and
(starving for fuel ). Its has deminished power,is getting lousy gas milage..and after warm-up, it misses alittle, at idle.

At 70 mph it seems ok, but still lags and has to down-shift alot more than it seems it should...it also seems to run better on hi-test right now..?

Help?

Tnx
KYCOL