wounder if any 1 can help my cosworth had a bad miss fire when it peaked at boost i got told off motor scope that i had to change my plugs. Replaced my plugs with chamion qc57c the miss fire at peak boost has slightly gone but still there and it idles realy rough. I rang motorscope back and they susgested regap the plugs so i did to 20thow but still no better can any 1 help cheers tony

 

what's the spec of the engine?

 

stage 3 i think it has a t34 25psi dark green injectors rs 500 intercooler thats all i no is that any help

 

the above that's hi lighted could be your problem as for your spec I'd use Champion QC 59C which are fine for up to 400bhp and the QC57C which you have are for 400+ bhp which you DONT have and when used in under DO/WILL give a rough tick over!

 

If you have not done anything about the igintion coil now would be the time to do so, with a group a as a minimum, if it still loses spark with this and decent plugs you MAY need a coilpack conversion but would not have thought so at this spec.
tabetha