intake or exhaust

which would help bring down temps more, an additional intake or an exhaust fan. i would be using a 4" fan for a computur. is it more beneficial to pull out the hot air, or suck in cooler air.

Pulling hot air out should allow cool air to be passivly brought in ? You need to get rid of the stale air & replace with fresh air every several minutes to get best growth. No one knows the size of your grow but a computer fan may work in a small box of some sort - depends on your setup . . .

Pull hot air out at or near the top, draw air in near the bottom. The negative pressure created from the exhaust fan will draw air in the intake port.