This is my arrangement, 6 port 0.3mm nozzles (for knock control), a 1mm jet on the rear turbo exit (runs hotter than the front) and a 0.9mm jet pre throttle body. All fire at the same time fed by a Shuflow pump in the boot.
I`ve set the WI to inject at 9psi upwards, as a failsafe my boost controller will only operate when AFR`s are 11.5 or richer, leaner and the car runs wastegate pressure (7psi).
What I`ve found is it takes roughly a second for the WI to hit the chambers and affect the AFR (I`m running 75%methanol 25%water), with this setup if the car runs lean due to WI lag or failure the car will never boost high enough to get into the lean/ agressive part of the fuel map. Seems to be a good way to go about it when the alcohol injected is relied upon as a fuel.
I taper the petrol/fuel off in the map from 9psi to fully alcohol saturated at 11 psi, so there is a gradual ramp as the WI comes in.
It works very well for me, had good results and no knock as the fuel and ignition maps can`t jump into a WI zone without there being sufficient injection first, before the 1 secong lag could set off knock in the engine. Plus if the WI tank runs dry the car will never hit over 7psi which is a "safe" part of the ignition and fuel maps.