My friend has this engine and it is behaving very "on/off", not progressive throttle action. I tried to ask which pipe he was running but he said it was just a Precirotate pipe, which leads me to believe it is a 2088 PR pipe.

If you want more smoothness, more linear throttle curve, less on/off behaviour, would it be a good idea to try a different pipe, or is it a carb-issue?

I was thinking it might behave better with an EFRA 2072 Go pipe?