Mr P. I am by no means saying they are not accurate. My issue is they are VERY slow to react to changes, ie loosing pressure and will not always show a 1-2 loose quickly. I have personally see two cars loose motors, both nitrous due to using them. After doing some data logging, and in car video I was convinced to loose mine. I have seen this with both the Longacre and Auto meter isolaters. Just my experiences.