3" exhaust on a NA car is useless. Anything bigger than 2.5 on a 3.5L engine makes no difference except you will get a headache from the extra noise.

Whatever it is you get for $600 won't give you more than 5hp max (except NOS). That is nothing.
Save the money and enjoy with something else. Go on a trip or something but why throw away money for nothing. It's just a car and you already have most of the bolt ons.

 

600 is not enough for a performance part that will make you happy, either save it up or dont just buy because you want to look for something bigger.

 

600 is not enough for a performance part that will make you happy, either save it up or dont just buy because you want to look for something bigger.

 

Get the 4.083 gears. You won't regret it.

 

Get some sway bars.