Stick with MT-90, since it's recomended for Toyota gear boxes. MT-90 is a little bit thicker then normal 75w90, which will lubricate and protect the sycros better. Go on Redline's website and go to gear oils, it will explain everything for you.
Lucas and Royal Purple makes good gear oil also, but do more research on these two to see which one is best for your car.
I have MT-90 in my GTS and it works amazing under high RPM's and normal driving