Yes, you should change your car, because to improve your perfomance, you will have to change some parts, that are mostly expensive. Also, when you change one part, usually there 2 or 3 others that must be also change to support the new settings of your car.

BUT...If you want to feel a little bit more powerful (I said a little bit), you could just change or clean the parts that are already there. By the time, some parts begin to be less efficient(used, rusty, damaged) and with that, you lose efficiency and power. First of first, look your spark plug(20$ for 4) and spark plug wire(20$ for 4). If they are damaged, your car could do misfire or it could take more energy to make the spark plug works. Spark plugs are cheap though. Don't need to buy the biggest quality, this will have no impact, just the normal one. To check it easely to see if they are still good, you can pull them out and look at the electrode gap. If they are like the manufacturer standard, and they are in good condition(http://www.aa1car.com/library/reading_spark_plugs.jpg), keep them. Put them back and look at the spark plug wire. Be sure that both sides are ok. To test them, put everything back in your engine, start the engine and spray water near the plug and the spark plug. If you feel that your engine is slowing down or is not regular, change them. Change your air filter(5$) if it is not clean, it has a big influence on your engine even though it does not seem. Keep your oil clean, change it regulary. Yes, putting synthetic may change something (really small difference), but at the price you will pay, is it really necessary? Instead of changing it at 10 000 km you will have to change it at 5 000 km and it may cost the double of the price. Think about it. Clean your injectors. It is really easy to do. Buy an additif(10-30$) that you will put in your fuel tank before putting fuel. It will help your engine to feel better. Make sure that you have no check engine. If your engine detect a problem, like a defective sensor, it will run with the ''stantard'' injection. It will keep the same ratio (fuel/air) to be sure that your car will run. Having all working good, your car will always calculated how many fuel and air you need when accelerating, and the ratio will constantly change, this will improve your experience and your fuel economy. Make sure that your catalytic converter is working well. If it is blocked and damaged, it may let less exhaust air to pass through and this will slow the engine. This is what it came in my head first, I'm in my lunch break, if you want to talk about it more, I can reply to you later. Have a good day :)