2011 6.2 Hard Start when Warm
 

Hi Guys,
I'm having hard time figuring out what's up with my truck. 2011 6.2 with 95000kms. Recently it's been having long cranks once warmed up.
Maintenance is all up to date and plugs changed out at 85,000kms.
I've checked the fuel pump fuse as I've heard that can be an issue on these, its good and no signs of burning/melting. Fuel pump primes every time I put the key in so I've tried inserting the key a few times to see if it makes a difference but doesn't seem to help at all.
I'm guessing now that maybe its a bad purge valve or maybe the check valve in the fuel pump. But it only occurs when the truck is up to temp. When it's cold it'll start great.
It all started one weekend when I let the tank get to about 10km to empty and I changed the battery out with the 850cca motorcraft battery. Doubt that makes a difference but the issue began the day after that. I was thinking bad fuel but I've had gas from numerous different stations since then. Returned the truck to stock and it made no difference. Once it's running it runs fine, idles fine, and has lots of power. No codes and good voltage.

Any ideas? I'm at a loss of what else to check before I just start throwing parts at it.