I used to sell water injection kits but have recently made it 'open source'. I think this kit is unique in that it includes an accumulator to prevent the pump for cycling on/off repeatedly, improving pump longevity. It also makes use of solenoids so that water is immediately available at the nozzle instead of waiting for the pump to make pressure. I ran this setup for many years on my 1991 MR2 turbo, and it is a very reliable and effective setup.
One thing that I would change is the nylon tubing - I would use braided lines instead. For the 1 series, I think it would be best to mount the tank/pump/accumulator setup outside the engine compartment protecting those components from heat/vibration. I would only mount the solenoid(s) inside the engine compartment, close to the point of injection. The pump used (Shurflo) has plenty of flow capability to handle multiple nozzles and sprayers for the intercooler if desired.
Hope you find this useful! I'm happy to answers questions about it!
http://lovehorsepower.com/joomla/ind...=324&Itemid=93
