If you are like most people on here you will get bored, that's why we add further mods always making our cars faster. That is something you will learn in time.
Unfortunately, where i live anyway, you are going to have a difficult time keeping up with allot of cars in a GT. Newer Cobalt SS's, srt-4's, accord v6's eclipses wrx's and a list of other cars will eat you even with a good amount of mods.
If you want a fast GP get a GTP, you can get one with decent mileage for 5k. Some people have gotten lucky and gotten them for as low as 3k.
Your first step is to learn a bit about these cars before you make a move or you will make the wrong one and waste $, it has happened to most of us already. As a matter of fact it even happened to you, that is if you bought the k&N. You could have made yourself a very good 4" intake for under $60.
Keep reading stuff in this forum.
Read this while your at it.
Read this while your at it.