I just installed my Mac long tubes with a Summit x pipe. The summit x pipe is built really well but does not fit Mac headers. After about an hour and a half of cutting, bending and welding I got it to work. Summits website doesnt say it is for a certain brand of headers so I didnt think about it not fitting until I started trying to install it. When I got finished and I was picking up my tools I found the instructions on the floor that must have fell out of the box. The instructions said the x pipe was for BBK headers only. So this is a heads up if anyone is planning on buying one.