I am having the exact same problems on a 2002 Dodge ram 2500. I will be following along to see if you come across the fix.

 

Fuel pressure ok, ignition checked on scope ok and and all sensors are doing what they should. Did a second compression test last night and found #1 cylinder has dropped from 180psi a month ago, to 140psi presently. A wet test brought it up about 7psi. It's gotta be bad valve seating. Seafoaming through brake booster is the only other factor here. Must have cleaned up carbon that valves were sealing on. Just exposed cracks that were already there. I'll never use it like that again. It's not setting any codes yet, but will only get worse, so am shopping for a place to replace heads.

Actually PSI dropped 20 psi on four other cylinders. Very discouraging.

 

The misfires at idle are slight. I don't understand why they disappear at 1500 rpms and up. Well maybe, because at 70 mph the valves are opening and closing like 40 times a second. At idle like 4 or 5 times a second.

 

A slight misfire is probably indistinguishable at higher RPM.

Odessa or Clearwater are you best options for heads. New castings, (better) pair for under 600.

 

Haven't come across the answer to the stumble and engine shimmy at at idle. Two shops have looked at it and with no confidence can they tell what to do. All sensors are doing what they are supposed to. They can't see it on their scope but they can feel it. Last place that looked at it said the fuel pressure was on the low end, but within spec.

 

Does the dodge dealer have more advanced equipment to diagnose whether this is a computer timing problem or a mechanical( weak valve springs or bad seating valves)? So far out of three scanners used only one could actually see it misfiring at idle. All front cylinders ,2,4,6 and every now and then 1and 3.
there is a pronounced tick over cylinder 2 and 4, listening on top of valve cover using stethascope. When it stumbles the rpm's drop about 50 rpm's.

 

Pull the valve covers and check the torque on the mounting bolts for the rockers. Check the springs as well.

Done a leak down test yet?

 

^^^ +1 time for a mech test on the motor, comp and or leak down time. Odds are it has cracked valve seats and or the head as well.

 

No,a leakdown hasn't been done even though time was scheduled three times. They all want to wait until it gets worse or they really didn't have as much time as they said, and the last guy referred, decided to go fishing and left his young helper to do what he was supposed to do. Am going to pull the covers myself and have a look see and recheck compression. My gut feeling is merc is right about valve seats. Will let ya know when finally get a leak down done.

 

Finally got around to doing compression test twice. Once at ambient temperature and at as close to operating temperature. Engine not warm all cylinders showed 180 to 189psi, with motor hot all cylinders were 165 to 175psi.
Replaced the fan clutch because it failed and was freewheeling last couple days. It was dragging the motor down before because the difference in power is like night and day with the new clutch. The slight stumble at idle is still there but was made worse by the bad clutch.