To cut a long story short...
My 93 (K) WRX is hesitating from about 4,500rpm's.
I put a post in General Technical but thought I would try here too.
Katana suggested resetting the ECU was my best bet, and some other people suggested otherthings but:

I did the ecu reset...no difference.
So...put a bottle of STP injector cleaner in and.... No different.
Prayed some Wynn's Injector Cleaner into the Intake etc.... No Difference.
So I'm guessing Plugs??
It's reaching 0.5 bar often and only about 0.75 the rest of the time! If I accelerate GENTLY, it get 0.8 ish almost ALL the time. But as soon as I put my foot down, it hesitates.
Anyone have any other ideas? Or does plugs sound likely??
Jon

check the small pipe that connects to the bottom of the black plastic swell chamber thingy next to the MAF. sounds like the pipe has become disconnected,or that the pipe connecter bit has broken off (its crappy subaru plastic and breaks very easily) which can be difficult to see. mine did this the night i bought it, and, well, lets just say i dindt sleep much that night. or the seventeen nights that followed until i found the cause.

go look now, bet youll find it off/ broken.

matt.

Cheers Matt!
But nope, that's all connected up. :(
Someone replied to my other post, had same model (Year etc too) and same prob, in same rev range, and his was due to plugs being gapped at 1.1mm not 0.7mm so I will check them tomorrow!!
Cheers tho, I'll know for future reference!! :)

Coilpack
Reduce plug gap to 0.65mm, if it makes a difference then you've found the problem.

Ok cheers!