I've done the modifications to my car bit by bit over the last year and a half. For engine mods I have a Apexi WS catback, AEM V1 cold air intake and a Unorthodox crank pulley. Not too much but yesterday I drove a friends stock TL, same year same AT and their was a significant difference. My car pulled MUCH harder than his did. Let me add that his car is in cherry condition. It was just nice to really see that money spent really shows.

 

Looks like you need some headers.

 

then you'll really feel the difference!