Another compression loss thread. Motor went from running fine to barely running during normal driving. Throwing a misfire code for #5 cylinder. I've pulled the valve cover and both valves are articulating fully and the valve springs are not broken. Ran a compression check, zero compression, no funny sounds. A rental borescope doesn't show the expected major carnage on the piston one would expect with zero compression. In the process of pulling the head now, because all the obvious things are okay. Any thought before I post results? Really stumped that this would happen with the easy life this truck leads. IF I'm lucky and I can get away with repairing/rebuilding the heads, should I do any upgrades to keep this from happening again?