I use to run DynaJets. Started out on the 3rd notch. MPGs were not happy and plugs fouled. The 2nd notch fixed about all of it. Also, check the pilot screws. Factory setting is 2 turns out from lightly seated. I always get negative feedback on the 2 turns claim but start there till you get new pipes when you can then fine tune the mixture.
This is where I run mine w/ stock exhaust and airbox/air filter. For the stock pilot jets (#35) my sweet spot with the air screws is 2 1/2 turns out - taking into account my present elevation.
Mileage is high 20s (if I ride them like I stole them) to mid 30s (if I keep near the speed limits).