If your planning on just doing a slip on exhaust you CAN run a bigger jet (IF YOU WANT).... if you also put a high air flow filter.....so the question remains... are you going to need to run more rich...yes... because you are allowing the air to go out quicker (less restrictive) you are going to have to feed it more fuel..... more fuel....more power... also what exhaust are you looking at??? also what year is your quad???
If you use a full exhaust on a stock motor you probably won't need a tuner with just that one mod. Depends on the exhaust though... anything marketed as hi-perf will slow you down and it will run like crap without building a motor that actually needs a better exhaust. Unless yours is rotted out, replacing it with an aftermarket is a complete waste of money.
Personally I think you’ll be wasting your money, you won’t get a great power gain even with a tuner, more than likely you’ll get a power loss. You got the wrong bike for power unfortunately.
Sorry to put a downer on things.
Remove the plug from the end of the muffler......it is noticably louder. Like others have suggested it will not be more powerful. Drilling some holes in the end cap cost nothing and will achieve a louder exhaust tone but there's no going back at that point. I mhave read some reviews where someone has put an exhaust and tuner on it and it gives about 3 horsepower and a few pounds of torque. These numbers are noticable but it come at a high price.........I think around $500 total.