Man, do you know what pistons you have? You'll likely need flat tops. I don't know that a Performer intake will cut it either, you'll need an RPM at least I'd think, a good single plane would do it too, like a Torker, but is it a daily driver?
With gas prices getting to be what they are, they were in the 80 cent range when I started messing around with this stuff and I hear it's going to be up above $3 later this summer.
Probably need to change the cam out, I've seen a lot of 'hipo' cams that are just old RV cams, a little better than stock. I'd probably put a spyder in there and go with a hydraulic roller and throw some hydraulic rockers on there as well. The less accessories you have will free up some HP, so you might want to go with an electric fan. Lightening the car up as much as you can is advised, so if you have a big subwoofer box, you might ditch that as well. Getting your suspension up to snuff will help as well, Opentracker's roller perches on the front and some Cal-Tracs in the rear will help with some wheel/tire combos that are light weight. Loosing the unspring weight helps.
You should be able to get into the mid to low 13's without too much expense, but a couple of mods and those guys are into the 12's.