[Spiegelglatt]

Great engine, crummy experience. Sorry to hear about this headache. Hopefully they find the problem because at this point I wouldn't blame you for ditching it (naturally would want it running to sell so you don't loose your shirt).

 

[Spiegelglatt]

How the hell did I miss this: had a sunroof leak.

Check all wiring and ECU as it is in the floor the water damaged the wiring loom and or ECU.

Should have caught that the first time.

Seriously, have them look into it and search on here (there are pictures even). This is a common problem, but mostly to older Tregs. Your symptoms even seem to match as all manner of hell and weird events happen when there is water intrusion.