300c 3.5 V6 Prins VSI1 Shudder and shutoff at idle.

Hi all!
My German is not so good, I hope we have some English speaking specialists here.
A Chrysler 300C 3.5 V6 with Prins VSI1 runs good on fuel with good mileage. On LPG starts well but often stalls after 30sec. If not, slight shudder on idle. Allso slight shudder on take off. When nice warm engine still slight shudder and less but some unexpected shutoffs on idle.
With Bexpro-NS and OBD software I notice short term trim on fuel +/- -3%, when on LPG short term trim +/- 5%. Iddle pressure 2.2bar. Tried to fiddle with RC_inj and Off_inj on idle (I manage to get short term trim to lower to +/- +3%) but shudder stays the same.
I should double check for vacuum leak, but 90% sure I have none (If I have vacuum leak I suspect it really tiny).
Allso trying to autocalibrate with Bexpro, but last part of the test, on idle, when softwre push to switch over to LPG I get ERROR and calibration stops. ( At this point I notice that the switch over to LPG takes longer than all the other switches. I have the feeling that's why I get an error). I have the feeling the engine cutoff on LPG is caused by some software issue, where some parameter shuts off the LPG. Allso very frustrating when this happens while in front of a stoplight...
Oh, and no fault codes.
I'm in the middle of fiddling with this system, so I can provide pictures, if wanted.
Really hoping someone could guid me in the right direction.
I can read a bit German...
Thank you!
Jo

 

Ich werde es morgen versuchen. Danke!