>>>*This is one I saw tested many times, even to a series of dyno tests on an older carbed 22R. The same results were seen on the EFI versions.

The factory manifold is excellent and holds the correct back pressure at the port exit to control crossflow at the valves. The stock exhaust pipe is a bit too small, a sacrifice the factory made for noise.

We found a 2" primary pipe size all the way to the muffler entrance, then 2 1/4" on exit all the way back is the best all around. Smaller restricts and some power/economy is lost. Larger frees her up a bit too much and tends to soften the lower end response. It's easy to do since a lot of mufflers are available this way right out of the box, directional flow gains are well known in the industry.

The small increase in pipe size at the muffler encourages directional flow since any restrictions or reversions in the pipe itself are always a detriment.

The drawback is the engine will make more sound, that depends of course on the muffler design, also.....*EB