i have fitted a bov valve now while ticking over the revs are raceing then dropin down like its goin to cut out i think its a air leak but i cant find where it is any ideas or tips

 

Welcome. Tried putting the original valve back on? Chances are your engine will run better with it than whatever aftermarket one anyway.

If you want any more specific help you need to give us some more info - what type/model year of car, what type of dumpvalve you've bought etc. If it's a vent to atmosphere type of valve, did you remember to block the recirculation pipe from the OE DV?

 

thanks for response iv got a 95 wrx 260bhp i put a bov turbo blow off valve not a atmosphere type yes i blocked recirculation pipe from the OE DV the fault is more noticable after the choke has gone off