I have the basic 1s and a single 1.0mm and run 12 psi on a compression of 10.5:1 no detonation and a/f under wot is 12.2-12.4 from 6000-7000rpm and from 4000-6000 11.8-12.1. On the 1/4 the car would pull gears hard all the way to 4th near redline 125mph(7000rpm) where I end 117mph at the trap.
There is a drop and no increase in temp from 1st gear pull to 5th gear 7000 on the highway thats 160mph
Another Bmw owner Boost M3 has a super charge setup running 11 psi on stock compression and with every gear pull to redline intake temp in the manifold dropped on average 50-60'F vs no water using a obd II scan tool.
There is no reason why you are getting increase temp on the higher gears. It does not make sense unless the water injection pump is losing pressure on the long gear pulls. ??
Check the voltage at the pump under load and could your pump be weak?
Another question are you guys spraying enough water at what psi are you triggering the water to come on maybe you can reduce the trigger point.
If you trigger late there wont be enough time to drop the temp steadily.
Water injection works that is a fact maybe its not setup right try and mix of methanol up to 50% to help evap the heat from the intake.