I would run an intercooler regardless if you are running 5 psi of boost, or even less.

New intercoolers are cheap $$ , no reason not to install one.

Just an example on an intercooler kit for $187.
http://www.ebay.com/itm/TURBO-CHARGER-IN...5762300&vxp=mtr

Compressed air from a turbo, even @ 5 psi is pretty hot & if running cast pistons, you need as cool intake charge as possible to prevent detonation & making the pistons let go/blow apart.

MBHD

12 port SDS EFI