Well, you do realise louder car is not really faster, right?
If you really want to see improvement, think of a tune. A decent tune, not the one that fits all.
Better yet - invest in spare ECU that will hold the tune.
Expensive - yes, but it allows you to go back to stock to see if problems, if any, are only due to the tune or elsewhere.
Muffler delete? Nah... but that is me.
If you really want to get something - you need a full exhaust. And again - good stuff. I am not saying expensive, but reputable one. The one that will fit.
Removing the muffler - you will loose the exhaust note. Car will be just loud.
If you’re not looking to do a full ECU tune, you should look into a piggyback such as Racechip. Easy install and totally removable if needed. Not the most power gain but definitely a good purchase. Check out Panda Motorsports.
Also, if your not already a member, there are some good resources over at forteforums.com.