this weekend my mates s2 turbo has developed a problem. its making a a tapping noise coming from the top end. its quiet on tickover but when you start driving you start to here it. its also lost power aswell and dosent seem to want to pull over 3500 revs. the turbo spools up but it just dosent go anywhere. this has happened since the knocking/tapping has a happened any advise would be appreciated. thanks

 

could be a valve

 

hes just had the valve stem seals done 2 weeks ago. ticking over its fine its when you go to rev it you here it or more so when driving.

 

Lifters?

 

hi ive a similar prob. does it do it only when accelrating engine revs in neutral, and when driving under load eg putting pedal down or going uphill? on mine it goes quiter once up to speed! Does it backfire when going downhill with no pedal pressed in gear?