shoots dude, I wouldn't even waste my time or money if the car is only a lease. Not to bring negativity to the thread, but unless your thinking about buying the car after the lease ends, I'd stay away from mods and save the money for other things. Not only that, but if you modify the engine, you give up your warranty and if the engine ever craps out on you, your ******. They won't fix anything under warranty and you'd have to pay out of your pocket. Once again, I'm not trying to break your balls or anything, but I used to work as a technician at a VW/Mazda dealer and i've seen this type of thing happen, and I know how bad it is when you find out everything is voided.
Peace.