I have a 1990 C4 (yeah, I know it's not a F-body, but it has the same engine) with a stock L98, and I'm planning to rebuild it. When I rebuild it, I'll be stroking it and/or installing water injection. Either way, I'll increase compression. My final choice will depend on how the price and performance numbers pan out.

I have a lot of questions concerning water injection. I've read from several sources that water injection increases effective octane by 10-15 points since it cools the cylinders so well. I've also heard that it increases horsepower as well by cooling the intake air temperatures, but that's only a significant effect with water/methanol injection. To clarify right now: I am not considering water/methanol injection - just water.

The highest octane gas I am able to buy is 91 octane, with the exception of E85, so I want to plan on using 91. If what I've read is correct, that translates to at least 101 octane with water injection.
I also plan to tune this car myself. I have no prior experience tuning, and I realize that it has a steep learning curve, but I'm always up for a challenge.

To start with the least specific question, would it be practical to use water injection to prevent detonation on a high-compression naturally-aspirated engine?
Does quench matter with water injection? If so, is a quench distance of .040" still optimal?
With 91 octane, water injection, aluminum heads, and a quench distance of .040", what compression is safe? I've heard people commonly say 14:1 on 100 octane, but that's for iron heads. Since I have aluminum heads and will have quench, I was thinking 14.4:1 would be possible?*
Would I need to use forged pistons for such a high compression ratio?
How much harder is it to tune a water-injected engine? I've heard that water/methanol is harder to tune because the methanol throws off the A/F ratio, but with just water I'm not sure how tuning would be affected.
Lastly, do you recommend a certain water injection system? If so, why? I don't want one too expensive, probably $500-$600, but if you think one that is more expensive is necessary, I'd be happy to hear it.

*I will be using the XFI 268 cam, so my dynamic compression ratio would be about 11.65:1 with a SCR of 14.4:1.

Thanks in advance guys. I really appreciate any help you can give me.