I think this is the only way to properly measure exhaust volume.

 

Yes.

Radio Shack carries a decent one. They used to have an analogue one which is what I've got, but they stopped making that one. Now they just have the digital one that's more money of course. I use it for setting up surround-sound systems. Haven't thought of using it for exhaust but that's a good idea. If you are going to get input from other people on exhaust volume define some standards. For example, 12" from ground 10' directly behind centerline of vehicle, etc...

 

well it's hard to trust what people say about exhaust volume, so I think its a good measurement device.