An earlier compression test conducted not quite 2 years ago, when the
problem first began, revealed only minor, seemingly insignificant
variances. What I did not realize is a 10 lb variance is considered
"significant" when you're chasing misfire problems.

Also my symptoms were a little misleading. The misfires were occurring
only at low idle, i.e., sitting at a light idling in gear. As long as you
could maintain the idle at or above 1000 rpm, the misfire would not occur.
Fuel pressure was good (52 psi)

Before the dealer tore it down another compression test indicated 15 lbs
low on #7 and 10 lbs low on #2 and 5 lbs low on #8. Thus both heads were
assumed to be "involved". I had recently had a couple instances of P0302
and P0300 though the primary problem from day one had always been P0307.

A combustion leak test also revealed #2, #5 and #7 sucking air past the
intake manifold gasket during the intake stroke. Bad intake gaskets?
Improper torque? Who can say.

Teardown revealed a cracked cylinder head with the crack appearing across
the face of the #7 intake valve seat (not repairable without replacing the
head). Replacing the other head vs sending it out for a valve job was
close enough to a push (factoring in the labor) that we decided not to
risk it and opted to just replace both heads. The tech suspected a
hairline crack in the right bank around #2 as well but said only the
machine shop would be able to say for sure.

Aside from the plugs, which got pretty badly trashed from the combustion
chamber cleaner, the rest of the ignition parts (wires, cap, rotor) were
done for thoroughness. The O2 sensors were at my option and no addt'l
labor, parts cost only, although they were considerably more costly than I
had anticipated. They gave me a 12/12 warranty on all parts and labor,
which is 9 months longer than anyone else was offering and a free loaner
car which no one else was offering.

Inarguably I probably paid to much and had some unnecessary stuff done,
but bottom line is it's fixed, guaranteed to be fixed and I didn't have to
get my hands dirty. When you get 5 months away from turning 60, major
projects like this seem to lose a lot of the glow they once had ;-)  Hell,
I stopped changing my own oil 6 years ago.

If you've done all the obvious ignition stuff, the TSB, etc and still
having the problem, something in the valve train is a strong possibility.
Try the idle trick.  Clear the code and then drive for a day or two
holding a fast idle on it when you come to a stop.  How many miles do you
have on it? My problems began around 75k.

If you mean the "shotgun" approach, yes, that occurred to me, but the
evidence of low compression kind of indicates they were sniffing around in
the right place. The cracked valve seat, altho an unusual place to see
cylinder head damage, was the problem and was evident to the naked eye
once it was apart and cleaned up a little.

The question is whether or not they should have replaced the opposite
head. Lets ask this group, when you do a valve job wouldn't it be logical
to do both heads? I think the answer to that would be yes. The additional
cylinder head (completely assembled) was $353. Can you get the valves &
seats done on one head then reassembled w/new springs, etc for $353. The
labor to R&R both heads was already there, wasn't it? So for $353 apiece
we get all brand new heads, valves, springs, rockers & keepers vs buying
only 1 new head and hauling the other one to the machine shop.

I think we did the right thing here. Likely didn't need the O2 sensors.

Question: Does a cracked cyl. head have any core value other than as scrap
iron?