I did a compression test on my T-type tonight and I got some pretty strange results. I did one about 2 months ago and all cylinders were between 150-160 psi. Tonight I had one as high as 160 and one as low 90 and a couple that ranged in between. This is a new comp tester, I borrowed a freinds last time, but this one I just bought and this is the first time it has been used. I blew a headgasket on the first GN I had and it read 0 on the compression test, but is is possible to be "somewhat" blown or leaking? Or is the new comp tester the problem, I plan to borrow my freinds and test them back to back. Anyone have any ideas? Thanks Steve