What you are looking for is called an LM1. It reads in real time, the exh gases and tells you rich or lean. If you buy a single setup, you will need to do 1/2 your engine, or move it from collector to collector to get both sides done. The best setup is a dual one, where you can see either bank by toggling between the sensors. They are designed to be installed in the collector to be very accurate. The further away they get, the more possibility of error. A very good tuning aid, but you will realize how bad carburetors really are once you get one...lol. I've used them before, but never bought one..so i cant really honestly tell you which is better brand wise. Even a single one can be better to tune with if you're not the best at reading plugs or "seat of the pants" tuning.
