Installed BSD on my 06 Focus ST two days ago and today was first day on the road.
Feels like engine responds faster and there is some extra vibration.
Best thing is the car sounds much better than before...much more "authority". I like the idea of an additional quart of oil in the sump too.
'06 ZX4 ST Black K&N Typhoon intake CFM BSD kit.
'08 ZX2 SES RED STOCK (Wife's car)
'07 ZX4 SE White STOCK (Son's Car)
'12 Fiesta (daughter's car)