I have never noticed a nickles worth of difference but I only tested with the OS .46La engines. I used several of them during my fun fly days, the LAs. I did remove them from all my engines though but just because of vibration and the gray slime that comes out of the muffler when the baffle gets loose. Other then that there is no reason to remove them. I think this would be a good question for Bill Baxter from OS factory support? I know I never did any serious testing and no longer have any of the small engines with that type of muffler.