What you're asking for is $10 per 1hp. This is something that is nearly impossible in a 4-cyl. It's very difficult for V-8, both small and big blocks. A new cam will do it, heads will do it, and nitrous are about all the options they get, and they have the cubes to make more power with less modification.
See what I'm getting at? For a KA, a N1 exhaust will give dyno-proven by 2 or 3 people, 10-15hp. For $500 new. Which is $50/hp. A set of cams will give you 16hp, for $590 from JWT. $36/hp. A home-brew P 'n P on the head will give very slight increases. And it's not free. You need to replace the head bolts and head gasket, along with the upper intake mani gasket, and middle gasket. Nitrous is about the only way you can get $10/hp, and you'll need a 50hp setup off ebay for $500. Don't expect the clutch fan to give more than 1-2hp. Don't expect the EGR to give 9hp. Ever. And don't expect more than 1-2hp on gutted/removed cat.
So.. there are your options for 10hp. You can find used exhaust for cheap (or free if you suck people off like Funk ), which will bring the price down. Other than that.. I don't know what to tell you.
-Jeff