Air intake restrictor, 250 buggy ?

Hey all,

Question: What is the restrictor guage/diameter/size ? to suit CFMOTO 250.

History: I got a new Atomic buggy, powered by CFMoto250 eng#2K160039. After removing the air intake assembly (too low) and fitting a snorkel with a dustbowl air cleaner, we ran into trouble getting it running again. Previous knowledge of the 150 GY6, I pinched the restrictor and tryed on the 250, fail! (would run, but not rev) I found a drastically smaller restrictor and off it went, but I've lost 10kph?

Thanx guys
NT