I was told i had an exhaust leak in my flex pipe, i want to get it fixed , but i want to upgrade the exhaust at the same time, I plan on getting a turbo kit, is the down pipe and the flex pipe the same thing, could i replace the flex pipe with a down pipe....what should i do? I can't afford the turbo kit yet but i want to fix the leak, and not waste money on somthing i'm not going to need once i buy the kit.

Usually some where on the down pipe there is a flex pipe to allow for engine movement. If you are going turbo chances are you will be replacing the header & down pipe-wait till you do it to replace the flex pipe. No sense in doing it twice.