[parmas]

Ok that's fine if it's for safety but too much water will bring the power down drastically.

Before we discuss about the plug gap, tell us how much water are you injecting vs fuel.

To know this you have to check fuel pressure at idle/fullboost example (Engine -10psi /Fuel - 30psi) / (Engine full boost 10psi / Fuel - 50psi).

Know injectors flow cc.

Know injectors duty example at 3Krpm and 10psi.

Know how much water flow injecting at 3Krpm and 10psi.

Calculate water vs fuel.

In my opinion:

If injecting 5-10% you are on the safe side but slightly loosing power.
If injecting 15-20%, power loss is felt so you must run lean and advance timing.
If injecting 20%+ , you don't need any intercooler at this level.