My 96 STI import recently had the engine rebuilt, reconditioned block etc and was running fine now its started hesitating when on boost when it reaches around 5000-5500rpm. It kind of missfires a bit and hesitates then carries on boosting, i've also noticed tonight when driving it seems to have lost a bit of power and everytime i switch it off something rattles underneath like a loose bolt in the manifold area, it's been run on v-power since i got it back and has been warmed up/cooled down all the time. I was told the clutch is on its way out and will last around 10,000 miles just wondered if it feels like its loosing power because of the clutch or something else?? Can anyone shed some light on this please?

 

Anyone...???

 

Sounds like the wrong spark plugs.
Rattling will most likely be the heat shield on the downpipe

 

Whats the best spark plugs to use?

 

if ur loosing boost after 5000-5500rpm then id say check the ur turbo for play in the wastegate or even the turbo shaft. Also check ur boost solenoid, sometimes if u put too much oil in ur car then this solenoid can become clogged with oil. spraying break cleaner in the boost pipes can clean it up.

plugs? maybe... try using ngk-r platinum tipped plugs. model number: PFR 7B

a weak clutch can give the impression that ur loosing boost, but this normally happens when the clutch starts slipping. To see if the clutch is slipping drive normally to 30mph then slip into 4th gear... put ur full foot down. if the clutch is slipping, then ul notice the revs will climb high without ur vehicle actually moving accordingly..

check all vacuum pipes for slight leaks or rips...

other than that may the force be with you..