IM so mad it wont start

Yeah. After I changed that most of my weird starting issues went away.
I would suggest making sure the o ring fits.
The one that came on my new regulator was actually too small.
It went in there. but fuel was blowing by.

Put the fuel pressure guage on the truck the night before. Start the engine, check your reading, then let it sit overnight. Watch the guage during the first start. If it doesn't have pressure soon after cranking begins, but eventually gains full pressure. The checkvalve in the pump is bleeding down and the entire assembly needs to be replaced.