I'm running a 11/14, and it rocks! Seat-O-the-pants dyno says there is a big difference! cost me $150 and a few weeks of grief, but well worth it! If you are on a tight budget, I'd recommend the 11/14 as you don't have to change much to make it run. If you have more $$ available, go with the 11/T-bird.
-Russ