Instructed the SM to do as suggested:

If the shop would do the leakdown test while checking for escaping gasses at the intake, exhaust, coolant tank and crankcase breather, they would know definitively if the leaking is coming from valve seat leakage, blown head gasket or piston compression ring sealing. Leaking from the crankcase is lower end, coolant tank is head gasket, intake and/or exhaust is top end/heads.

A squirt or 2 of oil into a low reading cyl will show if it's rings or not, a jump in held pressure points to excessive piston ring/cyl wear.

Instructed the SM to do as suggested:

If the shop would do the leakdown test while checking for escaping gasses at the intake, exhaust, coolant tank and crankcase breather, they would know definitively if the leaking is coming from valve seat leakage, blown head gasket or piston compression ring sealing. Leaking from the crankcase is lower end, coolant tank is head gasket, intake and/or exhaust is top end/heads.

A squirt or 2 of oil into a low reading cyl will show if it's rings or not, a jump in held pressure points to excessive piston ring/cyl wear.

Sorry for the delay, but I think we have all of the tests done that we can without completely disassembling the engine.

We had initially done both compression and leak down tests, the results of which we have already discussed. We have done further testing, including leak down tests top dead centre, middle and bottom.

We pulled the injectors and did a boroscope of the intake runner to see if there were any bent valves, or blockages, the valves look ok, no blockages were visible. Just to be on the safe side,
we also disconnected the catalytic converters to ensure they were not blocked, and did another compression test, same result. We also did the boroscope of the block, which showed scoring
on three cylinders, most noticeably the cylinder with 90 psi.

We then packaged up all of our findings and forwarded them all to BMW technical to review, just to ensure we had covered all of the bases. Upon review of the data, they indicated that we may get away with doing rings
and rebuild the cylinder head, but with no guarantees as to the potential longevity of the engine.

At this point I think the best option both financially and with respect to reliability would be one of the engine replacement options we discussed. To do any more diagnosis I think would be a waste of your money. We have
performed the testing trying to take every possible scenario into consideration, and keep coming to the same result. The leak down is too high, and the compression on all of the cylinders on one bank are low, with one being very
low.

If you have any questions please let me know. I will have my phone on all evening, so you can contact me anytime by e-mail.

I'm of a mind to sell it as it stands.

I am sorry & I really understand how you feel. After my third engine failed in my Z, (12k+ motor I built that was supposed to be perfect but was mishandled by the machine shop) I tried to sell it running badly (noisy main bearings) and was offered less than 1/2 of what the non motor mods were worth. I found an engine on eBay, installed it myself anf got full market value.

Food for thought.

GL with whatever you decide to do.

Wow Frank i'm sorry to hear this.

This is some shit. I cant believe this happened. I have this funny sensation these guys are full of shit. Leak down tests in the middle, what the fkuck is that.

Sorry to hear it has gone from bad to worst.

Any new updates on the X? It's been a while. Are you selling it or keeping it?