Theres rough idle, and theres rough idle

Blower surge, while sounding cool is a sign of one of two things. Either stupidity, because they want it to sound that way, or ignorance, because they cannot tune it out. It's terrible on an engine. It beats crankshaft bearings to death. It's a lot more violent than it sounds. I've built blower engines before and tuned that out.......only to have one customer insist that I did not. He kept blowing teflon seals off the rotors. Finally called me back and got me to tune it out. Never had another problem........until he blew it up runnin a Mopar. lol