When you adjust the TV cable, look for a 1-2 shift somewhere between 11 and 16mph at MINIMUM throttle. If it shifts at 16 mph and still feels way too soft, the problem lies elsewhere.
The other thing you are looking for is downshift. Get on a nice open road where it is safe to do a wot for a few seconds. Start moving with minimum throttle. Wait for it to shift into 2nd gear. As soon as it shifts into 2nd gear FULL THROTTLE it. It has to shift back down into first. If it does not shift into first gear, you need to push the button again with your right thumb(with the engine off) grab the little round tubelike slide and push it toward the driver's side about an 1/8" (this is just about 1 click).
Keep doing this JUST until you get downshift. Then recheck your 1-2 shift speed mph and make sure you are still somewhere in that "window".
If your's keeps slipping out of adjustment, the little plastic teeth inside the mechanism that the button on the outside catches onto to hold the adjustment have probably been worn out. Here's a pretty good indicator if that has happened:
Engine off.
Push the button and side that adjuster all the way to the driver's side as far as it will go.
Now slowly rotate the throttle with your hand all the way to WOT.
The little adjuster is supposed to "wratchet" out. A series of little clicks.
If it clicks a couple of times and then just shoots all the way over, there is your problem.
HTH,
Blake