1999 Jaguar XJ8: Possibly needs an ECM

Hi there. I just got a 1999 Jaguar Van Den Plas that another fellow more or less gave up on because he had trouble resolving the ECM issue. The vehicle is equipped for one type of ECM, an LNE1410-BE503, but was replaced with a BB103 model from the prior owner. The car seems to run without a discernible hitch. However, I have found the same codes come three times now within about 200 miles.

P1384 Engine Misfire (Twice)
P1396 Engine Misfire (Twice)
P1000 Fuel Air Metering Emission Control

I have taken it to a specialty shop that said it had the wrong ECM, but it's been all but impossible to find a suitable replacement. Apparently, I need a BE of the type mentioned above or a BF through BJ. On the flip side though, the folks who run the Jaguar recycling facility in my city say that the car would not even run if the ECM was not compatible and the dealership is in agreement with that statement. However I haven't heard as much of a tick so perhaps it may be a cam timing issue.

In the meantime, I have to say that the XJ8 is by far the most comfortable highway cruiser I've ever experienced. Right now I have a 96 MB Diesel, a 99 Passat 5-speed 1.8T, a 97 A4 Quattro, and the Jag. It's the second one I've had (other one was an XJ6L) and I hope it becomes a long term keeper.

If anyone knows of a good source for the ECM or would offer an alternative possibility for the engine misfires, I am all ears.

Thanks, and all the best in the times to come.