The KD tester utilizes a rubber hose and threads into the cylinder head and has been useless to me to date. Both of my testers utilize the Schrader tips. I trust the gauge that works for me and have tested approximately 30 saws, tired, saws, newly rebuilt saws, saws that I rebuilt and have run in the bush for extended periods of time and new saws. To my knowledge all the saws are stock. None have registered over 155 PSI. I did change seals in an Echo 500vl recently. I tested the saw prior to disassembly and it was 150 PSI on the money. I damaged the base gasket so I cut several of my own with the material I had on hand. The best reading I get now is 135. I will leave the 500vl at such until I find an OEM gasket to fit. Just my personal experience on the subject. I would be interested in further observations regarding same.:greenchainsaw: