[UFGO]

Mine is doing the same thing stumbles until about 3000-3500 and then surges. I have a Factory Pro jet kit and Hindle on my 98. Factory said it most likely the float bowl height. If it get worse as it warms up it's running to rich. Drop the float 1mm.

Actually, I can't really tell if it's worse at it warms up. It just seems the same. It was running well at low revs when I had the height at the stock setting which is 15mm. So...I probably have it running too lean. I'll let you know what I make out this weekend when I tear back into the carb again.