I just read that article last night. Very interesting. I was supprised the dual exhust y pipe to y pipe didn't really add much.
I also have the K&N and the synthetic oil. The only changes I have done so far and it does feel like the car has a little more giddy up.
2003 Tropic Green Metallic 3.8L V6: MGW Interior Billet Accessories (knobs and pony shift), Bullitt Fuel Door, Silver Bullitt Rims w/245/45-17.