I have a 2008 Kawasaki teryx after going downhill letting the engine hold back it starts backfiring an running bad in till I stop an let it set for a bit then it will run fine until I go down a nother hill what could be couseing it to do this ???

Just take it to Tommy's. They will figure it out.

If there's any exhaust locks, wish I'd say that are. It going to above the muffler. If not. Tune up time.

Yup it's time for a tune up

Sounds like the fuel is building up and burning hot to cause the back fire .I would take it for a tune up.