yea, headers and throttle bodys for the v6 are a waste anywhere near stock so dont do it.
The only engine difference in the 3.8 to the 3.9 if the internals of the engine, so if you ever built the engine you might care~ thats about it other wise its all pretty much the same.
Cold Air intake
under drive pulley (you get the entire balancer and pulley has to be impacted on not a big deal just FYI)
exhaust (true dual catback is the way to go! 2.25 pipe all the way back as well, like a GT take off factory exhaust)
lower it with wheels/tires
grill delete (mach 1 grill delete kit)
get a custom tune from VMP or someone similar
if a manual trans (i hope so) get a shifter (mgwltd.com) you have a T-5 transmission if manual
your good to go