my 91fx only runs good using wild cat ys20/20 ,and using a needle valve off of a 61 fx. the needle from the 91 has a blunt end, where as the needle of off the 61 is tapered all the way down to a point for better refinement. with that combination using a 13x8 apc i am getting just a little over 11,000 rpms. Dont know what speed that is, but it does haul ass in my Shoestring. Had that same set up in my midget mustang until it bit the dust.

ken