I have one, but never learned how to interpret the info it provides and never really cared. I just watch it in case the needle wanders out of where it normally is. Here is why: When I installed mine there was debate about where to put the probe: which runner or the collector. I forget the pros and cons of each, but I settled on runner #1. Then I f'ed up by cutting the probe cable to length...BEFORE reading in the directions that you're not supposed to do that! So, I've always thought my #'s we not very accurate and were not to be fussed over. Like I said, I just watch for big changes.
Curious how you would use a properly working one for basic street tuning though...thats probably what buickpower is wondering too...