How do you check compression by yourself. My freind has the probe you put into the spark plug hole. I read the compression check part on mkiv.com but there is a part thats missing. It says to disconnect the camshaft position sensor and solenoid resistor sensor. Then remove ignition coils and spark plugs and then to check cylindar compression (it refers to step 6 on EG-34). How do you do this last part. Do you have to turn the engine over a few times using the ignition key and take multiple readings at each cylinder with the tester? Also, what exactly is a leak down? Thanks.