Unfortunately it is more like engine, manifold, pipe, clutch set up, drivetrain efficiency, track size, track layout, track surface, and most improtantly drivestyle combo that will yield long runtimes.

The 9901 is supposed to be the long runtime with softer bottom type pipe. I personally like the 2096 and the 9853 pipes. I have all three and it is not always the 9901 that yeilds the longest runtime for every track for me.

Experiment. Because some pipes, you may loose a little runtime, but you may be generally faster around the track.