1993 Buick Century 3.3L V6, Vin:N

ok so my buick century will not rev up in the mid range rpm. it will do idle to 2500rpm but will not rev 2500-4200rpm, but revs perfectly 4200-5535rpm.

what happens instead of the usual rev is that it backfires and chokes but does not die.

I would have to conclude that it would be the fuel-pump but that cant be because it wouldnt be revin high rpm and mid rpm.

I tested the fuel pressure and came up with 36 psi when the operating pressure is supose to be between 40-45 psi. BUT if my pump were bad then my engine would not rev about the midranges like it does now.

i replaced the o2 sensor, fuel filter, spark plugs, spark plug wires, and air filter.

Does anybody else have any ideas because i just dont know what would cause just the midrange of rpm to act up?

Any ideas would be very appreciated because i am completely out of ideas...

The MAF can cause that if it's failing in-range...