hi , well depending what you want to use the system for.......and what are you running? if your running a standard vr6 with a few mods then no point running a charge cooler , and water injection would help with temps but dont think you would get much gain on a standard set up if you running a supercharger/Turbo then both are pretty handy i am in the process of installing both , but installing a chargecooler is not a easy job and can cost a bit.... charge cooler set up - £400 + water injection - £200+ to get the best gain out of water injection you would need to mix it with Methnol/ect which