[2.2 Straight six]

the reason you didn't find any change in the low and mid ranges is because your cat wasn't causing much backpressure there. it was only causing restriction at higer rpm, so you only get a difference there when you remove it.

depends what you mean by affordable, what's you budget?

you could get a new cold air intake and filter for ~$140, new exhaust for ~$250 and together you'd get maybe 15hp gain.

after the basics (intake, exhaust, chip) it gets a little more expensive.