I just got through upgrading my 7.3 filter head. I had a leaky heater, and a leaky water separator drain that developed after an injector swap. I could leave the truck overnight and when I would take the filter off, it would be an inch or more low of fuel. I'd say that is some air intrusion. I found that swapping the stock type filter for a wix 33417 filter eliminated the drain leak. I removed the fuel heater all together, tapped the hole out with a 1/2 in NPT tap. Then installed a square head 1/2 inch NPT pipe plug in the hole and now I have no more starting problems. I guess I should have taken some pictures to document this, but I am not patient enough. I want it fixed right now....