I'll second the don't bother. I bought an extrude honed lower tube and ported out my upper myself. I used an air die grinder with a cone shaped aluminum cutting tool and cut for hours on it. I then honed it with a dingleberry hone till I wore it out. A lot of work for nothing not to mention the mess of metal shavings everywhere. None of this did squat! My times at the track didn't change at all. Now that I've added the 85mm TB, etc., and I'm pushing 330hp then now maybe it's helping, maybe.