If/when I get the $$, I'm putting in the turbo. I don't plan to drag race, I would just like to have that boost when passing.
i just installed a Thunder header on my 5 tonight. its designed for the 3 but it bolts right up! the tranny is pretty much identical to whats in the 3. i'm thinking of adding a trans cooler but i don't want to screw with my warranty too much on this car. I/H/E and springs might be as far as i go.
from what i've seen, mazda3 catbacks will with a bit of modification fit the 5. i am going to try it as soon as i get my hands on one.