I have a 1997 Quest GXE, 180,00 miles, that gets a P0306 code intermittently.

Recent work done: Replaced plugs, wires, rotor and cap. It starts/ runs fine, but gets this code on occasion. I have not been able to re-license it due that reoccurring problem (Arizona strict about codes).

The code is defined as "misfire 1-6" or "misfire cylinder 6". I have also seen it listed as "EGR excessive flow detected" (which one valid?)

I have had the EGR valve off, cleaned it, tested its vacuum function (diaphragm moves when vacuum applied).

Also, I have run compression checks on all cylinders. I believe they were within spec (~ 100 psi?), but perhaps marginal. I will recheck. Also, neither catalytic converter ever replaced. Should I do a temp check to see if high temp is achieved?

So, it seems to run OK, don't hear a misfire, but the code says so. Could it need a valve job (or rings?) Thanks for any comments!