[JimD]

Another piece that is different in the higher rated N52s is the exhaust manifolds - there are two. Most people talk about the down pipes or from the downpipes to the exhaust tips but if you want the maximum hp, I suspect you need to also replace the manifolds (at nearly $1000 each).

So you could be talking about ~$500 for the multi-path intake from a X5 or 130i, possibly bigger injectors, and a couple thousand worth of exhaust manifolds plus several hundred more for the rest of the exhaust. You could thus end up with several thousand dollars in parts to gain maybe 40-50 hp.

If you really want to know which parts are different, put your VIN into RealOEM and open up another window where you put a X5 or 130i as close as possible in production date to your engine and then look up what is different concentrating on intake and exhaust systems. I think you'll find the cams the same but differences in the intake manifold, exhaust manifold, and possibly injectors.

Jim