Good afternoon everyone.

I have a 2006 3.5l with about 210k miles. The car went from driving just fine to throwing the random misfire code. I've replaced the 3 coil packs on the rear side, all brand new Bosch double iridium plugs, new upper intake manifold and gasket, cleaned the TPS, cleaned the O2 sensors. I couldn't find any vacuum leaks. What am I missing? I already bought a new y-pipe and main cat I'm waiting to install.

 

compression test... worn piston rings

 

Turns out my precats hollowed themselves out and clogged the main cat. That's what prevented me from being able to get the rpm's up and made it misfire horribly. Took forever to blow all that stuff out. Now it runs a lot better but still has a slight misfire. Last code it gave me was P0306 so I went ahead and replaced the coil pack on it. Still have a little misfire somewhere.
Had fun trying to get the idle relearn down after cleaning the TB