Help Please. Water injection help needed / hose routing

A friend has a Kaw 750Sxi with a Coffman's dry pipe with water injection. Does
it matter where you take the water from to inject into the pipe? He has a
t-fitting coming directly off the cold water supply line. Would it be better to
take water off of the hose between the head and the upper manifold where the
water is already heated? Also, how much will midrange suffer if you don't
inject water. How much will top end suffer if you run it wet?

Thanks,
Tim