WK stato LS1 misfiring and idle issue when cold

[WKStatoLS1]

Hey everyone,
i have a 2004 WK statesman LS1 and have been having a persistent cold start misfire and idle issue for a while now. i have replaced the plugs and leads as they were fkd and replaced the fuel filter last week and just replaced the fuel pump yesterday and it is still running like s*it when cold and idles erratically. I have had it scanned and no DTCs showed up whatsoever making my ability to properly diagnose this issue much harder. If i spray start ya bastard down the intake it runs perfectly fine so im lost a bit. if anyone can help me out with this issue i would much appreciate it as i need it running properly asap.

thanks

 

[HSV126]

sounds like a vacuum leak.

 

[VFSV6FORME]

sounds like a vacuum leak.

If you have a budget Vacuum gauge you should be able to pick this if i'm correct.

 

[BlackVXGTS]

How long does the misfire and erratic idle last for, before it performs OK (assuming it ever does)?