I thought i saw a little while ago that some one had tried it. Now i dont know if it gave the engine any consderable hp or torque. But usually the trx engines have the sleeve port a bit smaller then the exaust port on the crank case. So if you dare to you can do the sleeve work just be careful. if you want to see how much material you could take off take the engine off the car.

Take the header off along with the head, put the piston at bottom dead center then you can put it to a light and look through the exaust port or you could take a marker and put it into the exaust port and color the parts of the sleeve that shows then take the sleeve out and you can look at how much material you can take off. But i would not do to much off the top of the exaust port if any because you could change the timing of the engine and have it not work at all. Just make sure that when your dont to make sure the inside of the sleeve has no burs on the inside of the sleeve or have the sleeve not be smooth then it will scar the piston causing compression loss.