My GF's Duster 360 is slow as hell !!!

IMO, it's the taxi cab carb... then maybe the intake, street dominator?

It should be making around 320hp and maybe 350 with a decent carb on it. My friends Demon has a 9.5:1 360, xe268H , ld340 and 750dp and it makes right at 350hp. No reason that one with more cam/compression shouldn't be in the same area. His demon ran 14.20 at 103.5 MPH at Vegas with 2.76 gears and no carb tuning... carb straight out of the box.