Anyone know if it's normal to get a little backfire on a Focus RS after fitting a Decat pipe, Pumaspeed hi-power elbow and a large induction filter???
i don't get it in every gear but sometimes in 2nd or 3rd?? Thanks

 

Hello mate.
Don't know whether this will help you decide if you have a problem or not but;
My cousin has one of those new shape astra VXR's, the white nurburg type. Guessing the lump in them is fairly similar to your RS. Well, they have iirc a sebring stainless exhaust on them. I drove that. It sounds fucking throaty on the move, and spits and pops like a good un. I was well shocked (and smiling like a 10yr old).
Honestly wouldn't worry about it.

 

my 200sx s14a used to pop and bang very loudly... and that ran mint