are you serious?! haha well when you only have a m52 engine a m50 manifold is very special. it has like 60% larger inlets than the manifold that comes stock on cars such as mine. it is a fairly large increase in performance for a bolt on. the only down side as far as i know is that you lose like 1% power in your lower rpms but the rewards out weigh it. i have heard it complete changes your car.
Larger shorter intake runners, you get higher volume air flow but lose the low range high speed flow of the longer m52 intake runners.
Basically: m52 manifold feels faster on the street because your "under the curve" torque will be higher, but a m50 manifold will net you more dyno hp because at high high revs you'll make a few extra hp.
on the street i still prefer a m52 manifold myself, even if on dyno shootouts it'd make a few hp less.
if you want a bigger bore on your TB, you can check places like westcostriots. or you can get someone local to do it for you. its not overly hard to do but you should still find someone knowledgable enough to do such a task. and yes an m50 with a proper tunning will yield a decent gain.
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