From what i read here and elsewhere, this is the best solution for a faster bike without spending a fortune on a rare shimano freewheel,
http://www.ebay.ie/itm/DNP-Epoch-Freewheel-9-Soeed-11-34T-Nickel-Plated-/381155832626?pt=LH_DefaultDomain_0&hash=item58bea87332
Its for a 9 speed Carrera...