I have today taken delivery of a spare intake manifold, I have opened it up & intend to polish it inside & out. I have a 74mm throttle body (plus o ring), matching maf & also intend to fit a DIY cold air intake. Thought Id do all this at the same time. I am also going to fit an oil catch can, looking at the state of the internals, its really nasty, my question is - which is the worst polluter , the egr or crankcase breather?