i hav just fitted a screamer pipe to my 96 glanza v an it is now backfireing wen it hits about 5000 rpm,is this a common problem and how wood i go about fixing it any help wood b much appreciated other mods to the car are front mount intercooler,hks filter,full exhaust system and bov i also hav a turbo xs manual boost controller but is not yet fitted,would this b worth while fitting to the car and how hard are they to fit