I got my 3.0 re-mapped by MRC a few months ago - which gave me a worthwhile gain IMHO - it's not the sort of night and day difference you get when you remap a turbo, but it is definitely more sprightly, especially at the top end upto my higher 6900rpm redline. I was 5mph faster on the MRC test track at the top of the hill, so the extra power is there.
The stock v6 doesn't breathe all that well past 4000rpm so a better exhaust would probably help release some more power and let it rev more freely.
If you really want to sort out the v6 properly, I understand someone's done a supercharger installation -plug and play + 100bhp!