Isn't the "coasting richer" circuit in the carb supposed to add a fuel to reduce the lean condition on decel? The rest of the carb may be performing great but it may be worth checking the function of the one circuit. I think it's entirely internal on the carb and can't be plumbed wrong with tubing.
It might be the same issue causing the loud pop on Telly's 40 on shutdown.
'03 KTM 450EXC
"If you know what you're doing, then you aren't learning anything." - A. Lincoln