HELP!! A4LD in 93 Mustang slips badly in reverse when warm

HELP!! I have a 93 Mustang LX 2.3L auto with 85k. I installed a TransGo shift kit to the letter, according to the instructions. While it solved the stalling when put in gear problem, now it's very soft and slow going into reverse when cold. Once warm, I can't feel it go into reverse at all, but apparently it does shift since it moves back when I apply throttle, but it slips a lot, requiring me to rev it more than I feel comfortable. I've started parking where I can roll backward or drive straight forward. Before I had the stalling problem, it shifted into reverse very firmly. A bit too firmly, in fact. I called TransGo tech support, but they had no answer. The tech guy suggested changing the TransGo spring on the reverse servo back to the original spring to see if that would help. Of course, that would require draining all the fluid and dropping the pan again, which I really don't want to do without knowing for sure that is the problem. In addition, the Mustang is my only working car right now because my other vehicle has developed a severe oil leak, to the tune of over a quart of oil when I take my wife to work, a 12-mile round trip. I believe it's the timing cover gasket, which is a lot of work to change. Btw, it doesn't slip at all in any forward gears. Any ideas?

Update. Since I didn't get any responses, I thought I'd update. I took out the Transgo spring and replaced it with the original spring. I also reinstalled the clip that Transgo's instructions said to remove. No change, the reverse problem is still there. I'm baffled, since there was no reverse problem before the stalling occurred, and none of the other Transgo springs have any bearing on reverse. Does anyone have any ideas?

Well, I clicked on the link and found one guy who put in a Transgo kit and had a problem with reverse. He ultimately called Transgo and they suggested he put a 0.07" washer between the servo and the servo case. Apparently, that pushes the servo pin closer to the reverse band. I'm not exactly sure where he means to put it. Although no one at Transgo was any help when I originally called them about this problem, I'll try calling them again.

Since this only happens after the car warms up, my other thought is to add a trans cooler. I don't know if the car already has one of those trans coolers that are part of the radiator, so I will look tomorrow. I actually hope it does, as that makes adding an additional cooler easy, by tapping into one of the lines. If not, I would have to find a way to tap into the trans. If I can keep the fluid cooler, reverse will work, and cool fluid will extend the life of the trans. Right now, once it gets warm, reverse will not engage until about 3500 rpm, which is not acceptable. I have to park so that no one can get in front of me, which limits my options and is a hassle.