Nothing to do with your power source/HPA - you need to look into the hop unit and BBs.
Switch up to a .30g BB if you can and then consult any advice on adjusting the KWA Vector hop. There is the EVO II hop up set which might see a marked improvement over the stock one if it's anything like the MP7 one released, but my impression was that the Vector hop was really not all that bad out of the box.
Edit
To be clear: I don't claim to know a huge amount about it (the Vector) though - just saying that your HPA taps will have nothing to do with lack of range unless your fps/muzzle energy is all over the place due to a poor seal or regulator that's not refreshing quickly enough (but then you'd see your BBs going in all sorts of trajectories as they leave the barrel).
i'll look in to better hop ups ( can't say i understand what it is I'm looking at though)
Cheers!