I purchased a 2004 D2 with a rebuilt engine several months back. The engine ran well and made good power but had a check engine light with the following codes:

P300 Misfire detection. Multiple cylinders(Emission relevant) Maximum value exceeded. Fault present and intermittent.
P304 Misfire detection Cyl. 4(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P303 Misfire detection Cyl. 3(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P306 Misfire detection Cyl. 6(Emission relevant )Maximum value exceeded. Fault present and intermittent.
P307 Misfire detection Cyl. 7(Emission relevant )Maximum value exceeded. Fault present and intermittent.
P301 Misfire detection Cyl. 1(Emission relevant )Maximum value exceeded. Fault NOT present and static.
P308 Misfire detection Cyl. 8(Emission relevant )Maximum value exceeded. Fault present and static.
P302 Misfire detection Cyl. 7(Emission relevant )Maximum value exceeded. Fault present and static.

After doing a ton of research it seemed like it needed plugs, wires and/or coils. I have done the following work (in sequential order) to try and fix the issues:

-Replaced both coils (with genuine Bosch coils)
-Replaced spark plugs (3 times. Tried NGK then Bosch +4 now back to NGK)
-Replaced plug wires with Kingsborne 8mm wires
-Replaced all 4 oxygen sensors(with genuine Bosch sensors)
-Replaces crankshaft position sensor (with genuine Bosch sensor)
-Removed K&N filter, cleaned housing and replaced with stock paper filter
-Replaced MAF sensor (with genuine Bosch sensor)
-Smoke tested intake for vacuum leaks (no leaks found)
-Compession test (all cylinders at 165 to 175 cold)
-Tried 2 additional ECUs (no change)
-Replaced fuel pump
-Reconditioned and flow tested the fuel injectors
-New catalytic converters(they were in bad shape anyway)

The codes were reset after each step but returned. The P300 code has been present each time. The individual cylinder codes vary with at least five every time. I drove over 500 miles one time and 200 another (including the various drive cycles numerous times) in an effort to complete the drive monitors. 7 out of 8 monitors completed but not the catalyst. Then the check engine light returned.The truck has been at 2 Rover specialists here in the Los Angeles area recommended by the local Rover club without any solutions. They both thought it ran fine.

I can't get it smogged so I can't get it registered. The only suggested idea(from a third shop) that I have not yet done is replacing the engine wiring harness. This idea seems like it would be very difficult and is a long shot at best. Thoughts?

Other than the harness idea, any other suggestions? I am extremely frustrated and out of ideas. Thanks in advance!