check for burrs on the injector, the fuel rail (if that's the side that's leaking), and the intake. if you find any rough surface, clean it (small round file or fine sandpaper), but you'll want to try and vacuum it at the same time if it's on the intake side...
check everythin for burrs man, that's all i can think of unless something is out of round and you're now plugging a round peg into a oval hole or something like that...