I am going to have to say ProSport is correct. "every combo is different". I have seen motors on the dyno that make more power with a 4150 and others make more with an adapter and a 4500. Also have had motors that make more HP on the dyno one way, but run faster on the track another.

In my opinion, the 4150 intake with 4500 adapter is a better "general" combo as it helps improve mid-range and idle signals when driving on the street without giving up anything on the top end.

For race only applications this may not be as much of an issue.

Scott