they aren't noticeably louder either.... from what I can see the EFFRA rules are more about grabbing cash then they are about reducing noise... The guy who came up with the rule has next to zero scientific data to base his assumptions on and from the talks I have had with them have no concern that the legal pipes seem no quieter then the illegal pipes.... From being a track owner myself the only complaints we ever got were from the PA system, not the nitro engines..... I am blown away that American racers so willingly accept these European rules without question... willingly accepting that their nitro racing experience has been watered down due to some rules that really only apply to a very few select tracks in Europe, talk about the needs of a very select few taking precedence over the needs of many....