46u sorry i just saw pipe and figured tuned pipe.

I run this header.
[link]http://www2.towerhobbies.com/cgi-bin/WTI0001P?&I=LXFAZ9[/link]

I had to do some grinding on it and the ring where the spring hooks too. I pretty much cut a chunk of the ring out. 3/4 or 2/3 of the ring are left but it still holds and doesnt leak. The exhaust port on the enging seems pretty close to the pull stater. That is why i had to do some grinding and cutting to make it fit. It all works out ok though.