I tried a Mac's pre tuned pipe system on my TT .46 (Magic Extra) for a little while, but didn't like the poor transition. I tried adjusting the needles till blue, and different plugs just to see, but the lack of proper throttle response for hovering, and low inverted stuff made me remove it. The plus was 14,000+ R.P.M. w/ a 12.25X3.75 APC on 10%, and rocket like vertical, but for the smooth control needed for low level, and peace of mind, I went to an Aquacraft (Tower) muffler, $13.99...Annother reason I took it off was I was afraid of over stressing the tail/control surfaces w/ the sometimes sudden surges of power. I mean that sucker would really get rippin' if I wasn't really careful...