What type of performance improvements can one expect from a water injection system on a 13B turbo (10lbs boost on 110 race fuel)?

Any rejetting (blow through weber system)?

I used the water tank for the headlight washers from a 10AE. It holds 1.5 gal and it was made to handle Methanol. Close to the engine so no running hoses from back of car. Sits very low in the car too.

Intake temp charge should lower if not running an Intercooler, if running an intercooler you shouldn't see any temp rise when you nail it. You will also lower you're egts and be able to run a more aggressive tune. What is your complete setup?

In my experience I haven't had to rejet.