Cyl#6 has bad compression when motor is warm.
Cyl#4 has bad compression when motor is cold.
so maybe the head gasket between these two cylinders is gone. If I leave the plug in cyl#6, cyl#4 gets 120psi. and if I pull it out it only gets 90psi. I don't know how close the in timing the compression strokes are between these cylinders but maybe cylinder#4 dosnt misfire because its using compression from cylinder#6? I'm gonna pull the head in the morning!

 

ok I pulled the head off and I see nothing wrong with the head, gasket or valves. the cylinder does not look damaged or the top of the piston.

 

I guess all I can do now is put it back together and hope bad valve seals were my problem. because if the piece of metal I found in the oil pan was in fact a piece of a piston ring it was big enough to have surely destroyed my cylinder wall!

 

P0306 Solved. the fuel pressure regulator is bad and caused the wash of the top of my lower intake manifold. especially around cylinder#6. the excess fuel in cylinder#6 washed the oil out causing my low compression, misfire and P0306.




unfortunately i'll be installing new head gaskets, manifold gaskets, valve seals..etc. because I found that random piece of metal in my oil pan.

 

WOO HOO!!! That was a lot of work, but at least you found the root cause and fixed it. doctors, lawyers and mechanic's are a lot alike... we all practice our trade and hone our skills.
Tranzman

 

this sounds exactly like my daughters problem in her '05. Misses....coda said valve 6 issue, etc...thanks for the heads up!