Could fuel temp also cause this problem???...
When you're driving around the lines heat up a bit and the fuel expands... ...park it and walk away and be back in an hour and everything has cooled down and the fuel contracts in the lines...
I only mention it because my father would have a problem like is in his LandC' that had larger fuel lines and larger pump than stock... ...But you'd be driving around for quite a while, like a few hours without stopping, and it would be a bigger problem in winter...