performance chips

Depends on what your doing with your car, and what years is it? OBD1 or 2? I wouldn't buy a chip for an OBD1 car. Timing advancement and fooling the coolant sensor is mostly all the chip can do.

Would it be worth it to buy a new computer or chip for my 1987 Cobra Gt or is there something else I can do to the existing computer?

Save your money.

Haha alright will do, anyway the mods I have in mind right now are sub frame connectors, fender mounted cold air intake, and 3.73 rear end because I got a job at Canadian Tire I'll have money for my car :happyhapp

Save for a mass air conversion kit.

I read about converting to mass air before but the kit I found is 650$ http://www.latemodelrestoration.com/lrs.aspx?ref=mu&gotopage=/content_50_home.aspx so now I'm wondering if you can find a cheaper conversion kit and if not are the gains worth 650$?

you could buy everything seperately, like off of ebay used or something.
youll need the wiring harness, eec computer (a9p for automatic, or a9l for manual seem to be the best choices), and the mass air sensor. also the cold air pipe, since yours is a one piece, and the mass air one is a two piece.
you might be able to get everything for around 200.

To be honest, you don't gain lots of power by going with a maf conversion. It's more of a large supporting modification. Later on you can add a bigger camshaft and still maintain great driveability.

Don't get me wrong though, you can modify your engine quite a bit before a camshaft is really needed. I had a 88' convertible (speed density) with heads, intake , throttle body, exhaust done, and removed all emission equipment, and IMO, it drove better than stock. Once I bought this 89' (that has maf already) and put the trickflow stage 1 cam in it, it REALLY woke it up, even with only .500 lift . It has a nice choppy idle and sounds much more mean.