1. The turbo is a Toyota CT26. Which may make if difficult to just bolt a different turbo on. There may adapters to mate it to a big 16G or some other turbo charger.
2. The engine bay is not easy to get into. The access is small and located well inside the fenders. The room around it is not bad. So odds are that if you are short tempered and do not know when to take a break you will get ticked off.
3. The handling is very neutral, maybe not as good as a Miata due to the use of McPherson's instead of twin a-arms.
4. Having only test drove one, I am not sure of MPG's
What I do not like about the MR2 is how hard it is to get into the engine bay and the difficulty of making sure the right replacement parts are ordered. It is better looking then a Miata, but handling wise that is just not that much different. Cool air intakes are easy, just a little duct work would be all that is required for a ram air effect.
mr2.com