From my limited ownership and forum knowledge It appears you can possibly eek out a few horsepower from exhaust, intake, and NA chip, but I haven't seen much data that suggests (without an additional custom tune) you can get more than 10-15 HP from these plug and play mods.
it seems to me that if you really want a big jump, you have to go Forced Induction starting around 2.5k for a used older gen SC kit (kit only) or up to the 5kish for the latest brand new kit. Install is another issue entirely.
anywhere up to 1.5k I have been quoted for the install cost.
I would look for the forum thread about cost effective HP gains.