We were having trouble jetting a street Comet with a 34 mm Mikuni VM34. I rigged up an exhaust sniffer and after a few quick trips around the block (which is a mile X 1/4 mile) we had it pretty much dialed in. I have tried to use it on the TTR with a long 1 3/4 pipe but could not get a reading and surmised there was too much turbulence, hence the pipe in post #5, which made it come alive. I will try again one day and see if it reads better, but just been too busy to play with it and as there is really nowhere to twist the throttle around here on an unlicensed street bike so it hasn't made it to the priority list.