I would say there is practically no differenc between 2652 and 2660. It's on the Manifold you choose
#41615 (with 5 rings - short) for top speed,
#41617 (7 rings - long) for bottom power and
#41616 (with 6 rings - moddle) between the other two.

I'm mostly using the short one and here and there the middle one but never the long one. It depends on the track your driving on.