I just picked up a FASS ADJ 1004 witch is the adjustable kind I was wondering what is the recommended fuel pressure for a 12 valve with moderate upgrades and also should I go with 1/2 or 3/8ths fuel line I didn't buy this thing new so I don't have the install kit it comes with originaly

 

I would go with the 1/2" line just for the volume. From what I have read the psi should be around 20 psi at idle. Also you may want to switch to a torq technology fuel releif valve. If you havnt already. It helped my truck a lot idle a lot smoother and runs better

 

yeah an adjustable return line kit is a must ....

 

yes I am getin a torqtec ofv but the one I was lookin at isn't adjustable but it espiacialy for fass and air dog systems, so 20 psi is all I need at idle wont it go down as rpm rises I figured you needed more psi than that but I have never messed with a fass that replaces the lift pump all the ones for big truck you just add them to the system no adjusting necessary

 

i believe tork tec recommends 22psi at idle.