First off is it automatic or manual? If its auto its unknown to me, Manuals can be used from probes, 626, mx6 and mx3 only difference is gear ratios. However if its a manual and your having acceleration issues Ild find a worn clutch more likely than a bad transmission.
The problem with my car is that it revs fine but has no acceleration, so i would assume its a transmission issue. I found a fully rebuilt MX6 gearbox near me and i am wondering if its possible to put it in my mx3 1.8 v6 engine without having done a kl-ze swap as of yet.