I have a 1995 wrx import, manual , and have a few problems with flat spots etc. Replaced the coil packs and the problem seamed to go away.
Car seems extremely heavy on fuel even when driven gently. Noticed when pulling away from standing start when driven hard, when changing gear it's as if the clutch is slipping but its not(revs dont increase),when you back off just a little the power comes in and if fed in a little gentlyer it pulls ok. But now the car is knocking really loudly at 3000 rpm sounding like a big end.(so my mechanic says)
please any advice, what is maf sensor? where is it and what does it look like ?Can this cause this failure.

Managed to locate another engine but it has a torque converter (auto) is this the same engine as a manual?

 

Fuel issue could be MAF or Lamda sensor failure....

Clutch - could well be slipping

Big end failure is like a "drummer thrasing the drums" though usualy this is heard at just 1800 rpm

Get it into a specialist before you start buying engines......it may not be terminal

 

It does sound like that, will get it properly looked at. Ta