Having the same or similar problem with my wifes focus, its been like this for a while, cant seem to get to the bottom of this annoying problem, idle is ok but occasionally erratic, when accelerating in neutral it will go steady to 2100 rpm, I keep slowly pushing down the pedal and the engine starts to hunt badly then after a bit more travel it clears and revs fine, if I floor it it hesitates, there also appears to be a real loss of power when driving and its quite thirsty too, checked the plugs, air filter etc, checked the map, tps, o2 (b1s1/s2) and all ok, checked the fuel pressure reg valve on the end of the fuel rail thas good, ive also checked for vac leaks as in the pipes I can see and they are good but I can hear what appears to be a vacuum leak near the throttle body/fuel pressure reg area but cant see or feel anything, any ideas anyone with this cos its doing my head in now