All of our bikes are snorkled and have HMF pipes. We do not have the spark arrestors in them. We see no difference in needing any jetting or adjustments to the bike. Defintely hang on to them in case you ride in any forestry divisions ( ie.. Ocala National Forest..ect.. ). They wil require you have them. They are definately louder with them out. I had to put the one back in on the 650 Rincon. It was so annoying..I was getting pretty bad looks when I hit the gas.