I just typed all of this stuff to someone, so I'll put it in here. These apply to both the turbo and non-turbo cars.
1. Mod the air can.
This is one of the easy ones. Go to a local parts store and buy a k&N airfilter for a 90-94 Eclipse. After you do that, follow the directions on this page:
2. Remove AC Belt
This one is also fairly easy but only do it if you no longer wish to be able to use your AC. Find the belt that is driving the AC compressor. There should be a tensioner that is keeping that belt tight. Just loosen that tensioner and pull the belt off. I don't have A/C on my car so I don't know which bolts to tell you to loosen on the tensioner. If you really decide that you no longer want AC, then you can be brave and pull all of the AC parts. That will save you about 60lbs in weight off the car.
3. Replace all your filters
Your air filter should be replaced with a K&N filter. You should also get a new fuel filter and replace it.
4. Spark Plugs and Wires
You should be able to get these parts from your local carparts store for about $60 total. When you replace the wires, you just pull one wire at a time and put the new wire on there. DO NOT pull them off all at one time. Unless you have a manual, you'll have a tough time figuring out how they went back on there. For the spark plugs, also change those one at a time. You'll need a gap tool and a sparkplug tool to do this. Be sure that the spark plugs are gapped for your engine. I don't know the spec, but the parts store should be able to tell you. Also, be certain to use the proper sized sparkplug socket to remove the plugs. Don't use a standard socket, because they have a tendency to get stuck in the plug wells. When you're putting the new plugs in, don't tighten them a lot. Screw them down as far as you can with your fingers and just snug them with a small wrench. If you put a lot of pressure on them, they can break or get stuck in the head.
If you have something to add to this, let me know and I'll put it in here.