Eric,

I just ordered a Macs standard header for 91FX. It is same mounting with 61FX, but has larger diameter pipe for 90 size tuned pipe.

If you are done with the fuse, can you find out the header clearance? How far should it be from the fase of the exhaust port to the center of the exhaust header pipe?

I am not sure which one can fit in the fuse ( standard header 1-5/8", Long 2-3/8", ExtraLong 3-1/8").

I am still waiting for another tuned pipe to arrive. Hope it is lighter. Macs Quiet pipe weighs 180grams with mounting. Standard Header for a 90 weighs 83 grams with coupler.

That is almost 9.25oz.

I am also waiting for a reply regarding a carbon tuned pipe from Taiwan. It is very light and can be use on 140 also. I will post again when I finalize the deal.

Let me know