1" uni-pods will fit on the stock air box elbow.
Check the float level.
Read the manual (available on mra.org), jax express guide and freds guide (see wiki for guides).
How many miles does it have on it? I'm willing to wager it's the belt; I've seen a kitted, piped, carbed NU go from 30 tops to over 50 simply by replacing the worn belt. Take off the starter cover, if the area inside is covered in black dust your belt is probably shot.