You still have a very specific problem that was already pointed out but you haven't addressed - you have used the wrong transmission fluid. If you're having a problem with the transmission and you know of something that is definitely wrong, fix it before you move on with further diagnosis. You NEED to have the correct Mitsu Diamond SP transmission fluid in there - the same fluid is sometimes available at Hyundai dealerships for less money than what a Mitsu dealer charges, since Hyundai used Mitsu trannys in some of their vehicles. Wherever you get it, you need to change as much of the fluid as you can - a simple drain and refill will only change about 2/3 of the total fluid volume due to fluid remaining in the torque converter and transmission fluid cooler. There is a process for doing a trans fluid flush that involves removing the return line from the transmission cooler and running the engnine to pump all the old fluid out - I think there was a post here on the forum about how to do it, a search should be able to locate it. That procedure will remove more of the incorrect fluid than just a drain and refill will accomplish.