Q: i just got an mr-s and want a bit more power. now, honestly how hard or how expensive would this swap be?
A: I thought they had a 2ZZ to begin with... Anyways, if you really want a bit more power, go with a turbo kit. I think XS Engineering was prototyping a kit a couple years back with Sport Compact Car magazine (I'm sure its on the web, too lazy to go grab the issue, its in my archive somewhere...) which would be a lot cheaper, easier, cooler and faster than a mere factory engine swap.