real question is how much money do u have to spend lol, chances are if u just got the avalon u got it cause it was a cheaper alternative to lets say a already turbod car? well add another like 4k to turbo the avalon, more if u wanna swap the motor
^ + 1.
The 1MZ is a pretty reliable motor, so it can handle forced induction to a CERTAIN EXTENT. TRD made a supercharger for it but they are hard to find and a little pricey IMO. I would actually be more worried about the transmission than the motor. But like PhatRoyale sad, contact Tony the Tiger first.