please can you help,just got 92 wrx and noticed at about 4000 rpm car starts to missfire or hessitate and this can happen from 4000 rpm up to 6500 rpm at different rpm,also noticed that its not as bad when boost is turned down below normal thanks for any help. john

 

Sounds like the coil/coils struggling, try cleaning and reducing the spark plug gap slightly.
I've just fitted 4 Bosch coils, much better setup.

Mark A

 

I've got the same thing on my RB5 no2 and no4 cylinders have bad misfires, no2 does'nt fire over a certain rpm!!!!

I've just taken the sparkplugs out all are fine and set to .7mm (NGK PFR6's) puzzled and on the off chance i thought i'd disconnect my MAF sensor just to try it, and guess what runs exactly the same disconnected so it looks like my MAF's shagged, might be worth a try on yours if you have one

 

I had this very problem and i started by changing my plugs which did make a little difference but in the end i had to replace my coils and this totally sorted out the problem.

 

Ive been getting that... kind of splutters... if that is the same perhaps I can swap out my coils too... what dosh are we looking at for a set of those then?

 

I had the exact same problem.
I asked on the forum hundreds of times and tried every thing,(new plugs, coils, maf, all the sensors under the bonet) but in the end after 18 months and nearly selling the car i modded a uk300 intercooler to fit, put exhaust heat wrap aroud the decat downpipe and that made it 95% better. If you want to ask call me 0n 01427 628195 and i will help if i can.