My zetec s won't run right, tickover bounces from 900 to 1000revs, and until you hit 3000 revs plus it is v lumpy, its got a decat exhaust and 4branch manifold, also a performance panel air filter in the air box, also bottom of airbox is riddled with holes?? Is this normal or has someone butchered it? Only bought the car yesterday, do any of you guys have any ideas would be grateful of some hints and ideas cheers fellas