So my 4.2 supercharged was running fine up until about 6 weeks ago.

I did an oil service and noticed a split vacuum line to the LPG.

After replacing said line and doing the service it suddenly started doing long cranks every morning when I go to start her.

I really can’t see how what I did is connected?

Anyway since having the problem I had initially blamed the LPG so I have disconnected everything I can and disable anything else to do with LPG to rule that out. The fuel pump is only 4years/36k old so left that but did a filter.

It has decent rail pressure and waiting as the key is turned a few times doesn’t make any difference.

I should say that once started it drives exactly as normal as it should.

What am I missing here? Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF

Try resetting engine adaptations

02 sensors may have drifted way out of whack with the vacuum leak.

Just guessing here, but worth a try 👍

Forgot to say tried that multiple times to no avail - the problem was worse after running lpg which led me to disconnecting it but still having issues Current stable:
2006 BMW M6
2007 4.2 V8 S/C FF
Gone:
2002 4.4 V8 FF