RE: Jett 56lx / 60lx question
performance from AAC and ABC are about the same. AAC tends to be lighter.
Typically AAC cost a little more.
Rear exhaust with a full pipe is the maximum performance. But keep in mind - RPM is relative to the load. You will have to decide a bit ahead of time what size prop you wish to run. The pipe will be tuned for an RPM range (fairly narrow on a full pipe). Once set up your prop selection has to keep the engine in that range to run its best.
Bob