Throttle Body
 

I would like to purchase an after market throttle body for the MAzda 3..has anyone done this yet? If so what size did you get and how much horsepower did you add? Did it void the warranty?

ANY modification you do can void your warranty. It'sd up to your particular dealer though if they will warranty something or not.

to answer your question, there are no aftermarkket TB's for the 3 yet. The gains from a TB on a NA car are vey minimal at best (when talking about a low displacement 4cyl.). Focus on the smaller stuff first like intake and exhaust and give the aftermarket a chance to get into the 3.

yeah, TBs aren't going to help you unless you already have either nitrous or forced induction or you're bored and stroked.