Bigjoe,
Here is a picture I for my moosecan setup on my St90. On this header, I didn't cut any at all at first. I used the full 6" of the header, then my moosecan shown has a 1 1/2" piece on it. I was worried about the header being to short anyway, so I didn't cut off any of the header. But this is for my ST90.

On my 40FP, and other 40size motors,
I take the stock header, and cut 1 1/2 off the back. Then install that 1 1/2" piece into the moosecan. I don't cut and throw away the 1 1/2" piece. So techinally I am not shorting the length of header at all. My lenghts are the same. Maybe I am doing it all wrong. I will go and pick me up some 3/4" pipe this week, and try it your way, because, what I am doing isn't working out the way I want it.


As for the motors going lean, I don't think they are. I think its just the opposite. their going to rich. Because, I am having to lean out the motor untill I almost shut off the high speed needle valve.