[JimD]

I played with RealOEM for a few minutes comparing a 2009 e70 X5 n52 to my 2009 e88 n52 to a 2006 330ci n52. I was looking at the intake and exhaust. I previous compared internal parts (pistons, camshafts) of the e70 and e88 and couldn't see a difference. I confirmed what Stig said previously, the injectors are all the same. The intakes and the exhausts are different. To be more specific, the e70 and the 330ci share the same intake - exact same part number. The e70 is rated 260 hp and the 330ci 250 or 255 (can't remember). Both more than my e88. I think the e70/330ci intake is three stage and the e88 is two stage. All the exhausts are different. But looking at them, I got an idea.

The primary catalytic converter is effectively part of the exhaust manifold on our cars. So wouldn't there be aftermarket parts available that might also improve flow? I looked for the 330ci and magniflow makes these parts and claims higher flow. The set of front and rear manifolds is about $1500. I'm not sure 330ci parts would fit my e88 but it seems more likely than e70 manifolds would fit.

The advantage over headers is just clean air compliance. They are legal, in other words. You might get legality with even higher flow with headers and a catalytic in the exhaust tubing, however. But it seems like we ought to be able to get to the ~260hp level with complete legality with a new intake manifold and higher flow exhaust (need the cat back - magnaflow is around $600).

Jim