today I got the Treats universal black chamber for my '78 Gran Sport(noi), and I'm not schooled in the math of pipe tuning. It looks like it'll be easy to fab a mounting bracket, but before I do that I need an Idea of where to cut the stock header for max reversion. It goes into the stock muffler about 8 or 10 in. and needs to be cut at where the chamber inlet will be. So has anyone used this on a kitted garelli or knows how to figure the length?. polini iron 70cc kit, 17mm phbg, polini 18mm intake, unported kit.