Cheap, Fast, Reliable... Pick two.
Power steering and A/C delete, It won't be very noticeable but it will free up some power
Doing this is retarded unless it is an all out race car that you are trying to save weight on. The power steering only uses power when you turn and the a/c only draws power when its on.
But to answer your original question you could start with new over sized sized plug wires, new plugs, new rotor cap and button, intake manifold, header (but spend a few dollars and get one worth having), light weight flywheel, cams( if you kow someone that hasa b20 exhast cam its a little better then yours but i wouldnt pay anything for one), and good tune will help alot. none of these things alone will make a huge difference but when its all said and done it will be noticeable quicker.
I know it sounds dumb but if your into rollracing i would deffenantly get a solid fill rear motor mount,every car i buy thats the first thing i do. It puts more power to the wheels right away beacuse your motor doent have to move at all and you will take the hit for sure if your racing a car thats as quick as you. Something else to keep in mind is that in a 150-200 hp car every 100lbs=+-1/10 of a second in a quarter mile so weight to power ratio is huge and most people dont realize it.
I would stay away from nitrious unless you know what your doing especially with a stock bottom end, a 25 shot=weak sause, 50 shot=ok power gains, 75 shot=giant fail on stock bottom end. A 50 shot still wouldnt be reliabe and the power is only there whene you spray so IMO its not worth it, which brings us to boost. You could safly run 8-10lbs and with some time and know how you could peace together a half way reliable set up for a few hunred bucks and put 200-230 hp to the wheels and unlike nitrous the power is always there.
Hope i helped, Drew