Having built my fair share of race motors, your going to need more then just A PART. I assume you’re a young pup who is looking to show you stuff on the streets. While this is not my thing and I think you should spend a lot of time on the track I'll give you some help here. It's going to cost money and time to get what you are looking for. There are a lot of tuning sites out there that will tell you how to get the biggest bang for your dollar. My experience is in V6 and V8 motors on the classic cars. But the internal parts are all the same. Any internal parts you change May (and most often) require a modification to the Computer in the car. So I would check with a lot of the tuning sites and see what you can do with out changing the computer. Some good kick of points that are cost effective are replacement of the air induction system and exhaust system. The more air you move in to the motor the better it will perform. These can offer up to a 50 HP gain on the car. You never mentioned if you have a stick or an auto. If you have an automatic a higher stall speed on the Torque converter will allow for a better launch and should not require a change to the computer. Most factory converters will have a 1500 -1800 stall (the stall speed is where the motor will rev before the converter locks up and starts to apply power to the wheels.) In most the racers I build that are autos I put in 3300 to 3500 stall converters. This allows the motor to hit the wheels at the start or middle of the power band. If you have a stick this does not matter because you can rev and dump at your discretions. If changing the intake and the exhaust does not make you happy then you need to look at changing the inside of the motor. I would look at maga fluxing the head first before you do anything to it. If you detect cracks opt for that Hi-Performance head. If the head looks good on the flux then port and polish the head. This allows the air to enter and exit the engine better and faster then factory. Open up the valves about 1/8 to a 1/4 inch and go with a better cam and springs. (These changes often yield about a 30 to 75 HP change in the motor) if that is still not enough look at changing the pistons and the crank. Steel cranks allow a higher rev, are lighter then the cast and allow for better balancing to be done to the motor. Changing the compression on the pistons will allow more power and a better burn on the fuel but will also require a higher octane at the pump. If you like nitrous you will need to have the factory head bolts removed and new bolts installed. (If this is not done you can and often will bolt the head right off the motor.) It is also recommended to not run a high compression motor with nitrous as you will have a pinging issue and possibly blow the whole motor up. I have seen a lot of NA (Normally Aspirated) Honda, Geos, Neon’s, and Mazda’s blow the doors of nitrous injected cars when they have the motors and trannys built with the correct combination of compression, cam, and tranny. (A friend of mine races (Drags) a 99 neon 2.0 and turns an 8.35 at the track with out nitrous.) I know I have mentioned a lot here but it’s just to give you an idea and some knowledge about what you can do. Research is the best resource. Find your target budget and start building. Then work of that. It will take some time but soon you will have a car that will run well and compete at the level you want.
Also,Intake and Exhaust: A different camshaft is only one way you can alter the intake and exhaust properties of a vehicle. Actually altering the intake and exhaust parts themselves is another. While technically part of their own system, intake and exhaust modifications deserve some mention because they are intimately associated with the engine's performance.
There are two ways to improve intake efficiency. One is to allow the car to take in more air. This can be done is many ways, but is generally achieved by using a high-flow air filter or a shorter intake assembly. K&N air filters are great options here, because they drop right in with few tools, are cheap (only $50 or so), and are reusable so they pay for themselves. A K&N air filter will return about a 2-5% increase in horsepower, depending on your vehicle.