[cobrashoch]

Bruce Edwards has got it right. In addition to the type and design of the sensor you are using, you have to remember what the placement means. For example a header collector sensor will only tell you what the overall running condition is of all the slugs running on that side (bank) of the engine. A sensor on each header exaust tube will let you tune each piston independently too. So you see, it could get quite complex, dependant on what you are trying to do. Most of the guys that I know that tune using a sensor(s) use the early Mustang sensors. Bosch seems to be the make mentioned most often. Time to break out the welding torch.
cobrashock