Diag help? Dealer has no idea!

[HellRazor35]

2007 X5 E70 3.0 91k

Daughter is at school with the X5 a few weeks ago has to have it towed to the deal and have the Waterpump and Thermostat replace. Then a week later when the weather started to get colder it started running rough. They finally it would stall when coming to a stop at a light.

Now it starts and rough idles, throws a check engine and goes into limp mode and dies.

So back to the dealer and they had to replace the all the plugs as they said they were fuel fouled to get it to even start and are still not able to keep it running more than a few minutes

Saying they ended up doing a compression test and leak down.

3 of the 6 cylinders were between 60 & 90. Then did a vacuum check and this I did not understand. Said that air pressure was coming out of the gas caps when it was removed??

Said that they can try and use some special additive that could help with the compression to at least get is running so they can further diagnosis the issue and that possible that the bad leakdown was a Red Herring???

Any thoughts on this. Really frustrating as I am a plane flight away from all this

Any thoughts or experience with something like this would be great