I like my Mac's black pipes and for 3 reasons I believe are 100% correct. 1) They look cool! 2)They are seamless so, no leak potential. 3) The make a great handle when cooled down. I'm serious here! There may be a gain in RPM but, I don't think it's significant enough to warrant one on that alone.

Jim, the only engine I saw benefit with the black pipe is, oddly enough, an OS 40LA. A friend has one on a SPAD Debonair that is really heavy, and it just amazes me how well it pulls that brick around! Of course, it may just be my perception. Your mileage may vary....

True tuned pipes, as I understand it, can be tuned for a specific RPM. That may be high or mid or even low RPM. Unfortunately, when operating outside of it's selected RPM, a stock muffler will probably outperform it. This is based on reading and transferral of motorcycle technology. I haven't actually done this on a glow engine.

Interesting thread!