Dennis, Maybe a better question is why the port side is already 13/32 or .406 and the Stb. side is smaller in the first place? Buy drilling the Stb. 13/32 or .406 it makes the same as the port side. When I did mine I checked it and the port side was already .406 and had to drill the Stb. to make it the same. I think I'm confusing myself now. :) Doug

LOL. I think I am understanding now. Do you have any photos of your finished product? Thanks for shareing your knowledge it is most welcome.

I don't have any pic's at the moment but I have to take the boat outside to move stuff around before winter and I'll try to get some then. I have to credit Don Carter from Offshore Performance Specialites for helping me with this. The parts pic is also his work, he gave me permission to post it. I wouldn't have known about it all if I wasn't scratching my head when I went to plumb the new headers. Doug