i have a 97 sti type r and when ever i try to nail it it starts misfiring at 4000rpm but if i take it easy i can get right up to 7000rpm no problems does anyone have any idea what the problem causing this could be?

cheers

 

sounds like plugs or leads..

check plug condition and plug gaps.

Simon

 

i had the plugs out today and gave them a quick clean, they were a bit rusty? i didnt have leads to try but the ones that are on the car are only 8 months old about 5000 miles

 

do you use octane booster? leaves an orange deposit

what make of plugs and leads?

did you check the plug gaps.. need to be around 0.7mm

Simon

 

ngk plugs checked the gaps and they were all 0.7 yeah i use nf boost, not sure what leads is on it. just thought it was wierd how if you drive it sensibly its ok its just when you put the foot down that it misfires, would it not do it all the time if it was a lead?
thanks for your help

 

A Weak spark would show up under load surely.

 

ok, cheers what would be the best leads and plugs to go for? wheres the best place to get them from