I have an 05 grizz with hmf full system and a kn air filter. I'm running a mikuni 180 main jet, dyno jet needle at 5th notch, and 2.5-2.75 turns on the mixture screw. My plug indicates its lean(very white). On decelleration, theres lots of popping/backfiring from the pipe and the carb sometimes pops on the deceleration. Is it bad to use stock jets with dyno jet parts? What other carb setting combo's can i try. btw i'm at sea level

 

First, using stock and after market jets wont hurt anything, except if you mix and match on the needle circuit.The needle jet, and the jet needle, need to be matched.Either both need to be stock, or both need to be aftermarket as a pair. The pilot ,main, and starter jets, can be of any brand and not hurt a thing. Jets are just plugs, that have a precision hole in them. Be aware, that the numbers on a stock jet, may or may not relate to an aftermarket jet.
Its very difficult to do a plug chop on an auto, and with todays gasoline, and all the additives, its almost meaning less. A better way to jet, is to go by the drivability synptoms. If you have no symptoms, you got it jetted correctly.
The popping and backfire is due to a lean idle circuit. You can keep going out(richer) on the mixture screw, until you get to about 4 turns out from lightly seated. If it still pops and backfires, and you are at the 4 turns out, then you need a bigger pilot jet.
You can confirm its lean, to see for your self, by pulling on the choke, just before throttle letoff. This will richen the circuits, and the popping and backfireing will stop.
You can use the choke as a troubleshooting aid, to help figure out the rich and lean of the circuits.
Heres a good article on jetting, and it lists the symptoms of lean and rich, if you have anymore questions, keep asking.
jetting