I recently installed the BBK 66mm unit and regardless of the debate in power gains I would recommend this to everyone. Throttle response is so much better at all rpms, the car just feels more willing to go. Not to mention that the stock throttle body is so poorly designed the inside flap is thick and curved Restricting airflow.
If you don't want to pay 250 for a CFM goto eBay and buy the 66mm SVT focus throttle body from BBK it is posted as a buy it now for 250 or there is an option to make an offer. Both sellers that have the make an offer option accepted offers for 200.
03 Ford SVT Focus - Toms tune, Steeda mounts & stress bar, ORP, 66MM BBK TB, CFM UDP, Rota Grids
The Bad Cat (97 Merc Cougar XR7) - Flowmasters, MSD ignition, K&N intake, 19" Stern ST-4 Warps