a bloody good serivice with mobile 1 or alike oil ,a decent K&N no ebay sh*t and a free flowing exhaust, like some 1 has allready said the cats do soak power ,but then bear in mind will it have to be road legal?

i think the 2.5 manifold conversion will go on the 320 323 and 328i that will yeild more gains ,follow that up with a chip/re map and you laughin