Reasons for pulled timing after 5k RPM's?
 

What different factors would cause the factory ECU (EcuTek flashed) to pull timing after 5K RPM's? My tuner and I are pulling our hair out here. The car is an '05 VIII with a brand new IX turbo, 264in/272ex cams, Walbro 255lpm, 720cc injectors, MBC @ 22lbs of boost, and a TBE w/test pipe. The car has passed a compression check and leak down test with flying colors. The spark plugs are brand new. What are we missing?

any way of monitoring fuel pressure? Could be a weak pump or a poor connection in the fuel tank not allowing the pump to supply regulated fuel pressure to the injectors, but something less.

Would poor fuel pressure be reflected in the AFR?

Your timing is probably to agressive and you might be knocking after 5k so the stock ecu is pulling timing.

Put a splash of race gas in the tank and see if the problem goes away. If so then you are too aggressive on timing.