Originally Posted by sc00by4life
if you're only looking for 320-350, an evo 3 16g will do the job just fine.
^This. If you can find one.
As for the coil overs, don't get them. If all you want to do is go a bit lower, just find a nice spring/strut combo. Unless it's a car that is tracked every other day, coils aren't worth it (and maybe not even worth it either in this scenario).
But as for the TMIC, go for it. And yes, to see any benefits you'll need a new tune.