That's interesting, because I've had several snowmobiles from a '77 340RV to an '86 Formula Plus that all had just as good throttle response from round slides as my Mach Z has with flat slides. I would expect a much bigger difference with a lighter flywheel than a different carb. Much less expensive, too.

 

Check out e-bay from time to time, i got my 38mm TMX flatside at a very good price. when i went from the stock carb to the 38mm there was a very noticable difference in response. off the line i was getting the hole shot to the first turn over some 416ex's after the carb change, it made a big difference in my case. When trail riding i notice the difference when coming out of a tight turn and then hitting a big hill- it pulls hard and fast soon as you hit it.
hunt