With regards to amount to inject bear in mind the SC will just vapourise nearly all of it unless pumping massive amounts in so adjusting the tune probably wont be needed.

All you doing is cooling the intake by directly cooling the SC. If running a centri or a turbo as it goes after the heat problem then yes re-tuning would be needed.

Big thing is dont map the car to use the water/meth injection as if the system fails engine might go bang.

Thought you had a TVS! Whats the current set up with the 122?

If purely after cooling just inject water, Global-i got excellent results doing just that at T/R on a very hot day so id forget about the meth, unless doing something like T/R again or Vmax as the extra octane or two wont go down badly.

So is that 6 or 9psi pulley on the Batty spec?

Depends where the intake temp probe is. Before or after the injection. Obviously you want the temp probe to pick up temps after injection.

Summary: FI is bad for your car and your health

http://www.youtube.com/watch?v=Ku7TdLeEGsQ&feature=related

As others have suggested. Using WI can achieve various things depending on how you use it.

In low volume 100% water injection setups minimal re-tuning is needed, especially if it's only for safety. But often doing so can see a loss of power. But it will see cooler temps, and a much safer engine. Again this will vary from setup to setup.
But using it will often allow more timing and to run leaner mixtures, which will then see a restoration of power, or possible gain in power...and safely too.

Again, it is all very dependant on setup, boost used, compression ratio, intercooling, fuel used etc etc etc
And of course the amount of water used. I already covered it all before in other threads.

Add the poisonous methanol to the mix, and tuning becomes more critical. Simply dumping water or meth in and doing nothing else will not yield more power. But re-tuning taking into account the added octane, chamber cooling, charge cooling etc etc will yield more power.
But again, that's down to how good or bad your base setup was in the first place.

If your intake temps were good, your engine not knock limited in any way, then using WI is a bit pointless. Few engines fall into this category though.

And again...yes pure methanol is very poisonous. Never ever ingest it, and even skin contact is bad. Wash off immediately. It does also burn with an almost invisible flame. Certainly invisible in daylight.
But it is extinguished with water safely unlike petrol.

Indy cars run on methanol, and I think some speedway motorbikes run on it.

And it's much cheaper in 40gal drums than in small 20litre containers.

only going to 8psi

I've used home made WI systems with good results. IAT's plummet really quickly. I also used a simple Edlebrock set up which was load and rpm sensitive. It was pretty decent but unsophisticated. It's obsolete these days, lol. A friend used meths and one sunny day after a bit of boost he saw the bonnet of his car buckling and the paint blistering. The invisible fire wrote his car off. I'll stick to water.