Ok guys, here's a better summary:
1) I got fuel
2) I got sparks
3) Cylinder #1 = 140, #2 = 140, #3 = 0, #4 = 125
There's no weird noise, everything is turning fine, no smoke, the spark plugs don't show any bad sign.
What's the easiest way to diagnose a bad valve or holed piston? Can we check the piston with a small light thru the hole of the spark plug?
I know that I'll have to open it anyway, I just want to start shopping for the necessary parts. What are the next steps and how much am I looking to spend for each of the possible culprits?
Ho by the way, yes I was running a bit lean.