How can I make my 3.1L fast for cheap?
Understand that this engine is not a 'performer'. But here goes, in order of economy fixes: 1. Get a cold air induction kit. (AirRaid, K+E) Adds maybe 10 HP........2. Get a performance chip upgrade, but use caution. There is a lot of cheap junk on the market that won't do anything. Can add 40+ HP but will kill gas mileage and might force you to use hi octane gas. Try Jet Performance........3. Get a cat-back exhaust system. Adds maybe 10 HP, but if you already did the cold air package make that 20 HP. Try American Thunder.
How much would the chip cost?
there is no way you will get 40 hp out of a chip unless it is a turbo diesel. on a v6 you might get 15hp if you set it to run on premium fuel all the time. an 10 hp for the intake + 15 hp for the chip + 10 hp for the exhaust will not make 35 hp. it will make more like 25. it is not a cumulative thing. all this is assuming your car is properly tuned. and it still won't be fast.
Now with the exhaust. Would I have to take the cat off and run straight pipes?
Keep the cats. You're looking for a "cat-back" system.
What is the best place or website to find it?
Summit Racing or Jegs. You can also go direct to Magnaflow (pricey) or American Thunder (pretty decent). Try Summit first: http://www.summitracing.com/search/year/1990/make/pontiac/model/firebird/department/exhaust/engine-size/3-1l-189
Looking for a Used Firebird in your area?
CarGurus has 893 nationwide Firebird listings starting at $2,995.
Search Pontiac Firebird Questions
Pontiac Firebird Experts