For future reference, too late now I guess, a compression test can be done without even getting yer hands dirty. Its simple really, any competent TECH should know how. With an oscilloscope. 1 channel goes to a non contact amp probe, clamped around the starter wire, 1 channel to a crank sensor, or injector wire, if electronic. The amp clamp measures the amp draw in milliseconds, while the crank sensor measures witch cylinder is on its compression stroke. Takes 10 seconds of cranking, then look at the graph, line up the injection pulses, or crank signal with the corresponding cylinder, and look at the amp draw of each cylinder stroke. It won't give you a specific psi, but it will tell you if they are all the same or not. If one is low, you will know witch one by the crank pulse, or injector pulse. Easy peasy. Done it many times. That way it takes 15 minutes, your hands don't even get dirty, and you can tell the customer if they should proceed or not.....
I was a TECH at one point...... I have many tricks up my sleeve
Dew eat.