I did the stock muffler mod with eleven half inch holes and 1 1/2 inch tail pipe. Sounds great and have virtually eliminated the bottom end bog on take off. I also did three 1 inch holes in the air box. Stock foam filter.
Others have said no rejetting is needed and have found this to be true. I would like to ask if anyone knows the stock air screw adjustment. How many turns out? I have been fooling with it and would like to return it to stock.No matter what I do I still have sooty deposits at the tail pipe opening not much but enough to rub off black on my finger. Any sugestions or is this normal? My fuel economy is great with over 3700 miles on the bike.

 

The factory setting is 2-3/4 turns out.

 

I put a 162.5 main jet in my buddys grizz and it seemed to work alot better.We also had the air box lid drilled.We didn't touch the air screw setting.