They really aren't all that IMO..... i mean you can feel the added low end grunt, but up the revs its much the same as an intake plenum! Not worth the huge expense, especially for me running short gears as i will spend most the time over 5k on circuits
Had a measure last night, the mugen intake is 3" at the velocity stack outlet from the filter, never knew that think it should flow plenty combined with edelbrock 65mm TB and cut/port/weld inlet manifold
can anyone confirm that AEM V2 is the best cold air kit.