Whichever one fits on the SR20DE-T that I just put in my Focus for no good reason.
Seriously, I'd probably keep the UDP setup. TB would affect driving in traffic, chip would require premium, and the 2.25" exhaust (you mean a straight pipe
) would be darn loud. Even if it was a matter of going from a 2.25" cat-back (with high flow muffler and resonator) to stock, I'd still stick with the UDP. Doesn't encroach on fuel economy (helps it if anything), doesn't require premium gas, and is a "full" solution (not like opening up the exhaust while leaving the intake stock).