Gas also, Seems like some gas does it more than others. When I tried a lower octane mine popped more than when I used 93. When I went from the brand of gas I usually use, and was dang near empty on a short day trip, and bought a different brand, all 4.3 gals of it, the popping decreased drastically. I am guessing the different additives, anti knock crap and such made a difference.