hey go to turnermotorsport for cheap injectors that are slightly used. They sell the used one for $113 for all six. Basically, turnermotorsport suped up their e46 so they can race them. in return the sell off all the OEM stuff for dirt cheap.
As for me, I went with buying all 6 brand new injectors from circlebmw. I wanted that "brand new" peice of mind. they cost me around $100 per injector.