Tranny shifts too high

[Tooky]

Hi I'm still trying to fix my transmission.  I have 100K.  Ever since I got the car at 96K, the tranny shifts at 6100 RPMs in 1st gear to 2nd gear shift, +/- 200 RPMs.  Way too high.  I looked at my vacuum modulator vacuum T thing and the 2 little lines connect to the hoses and the big fat one is open.  I took the piece off and blew through it, the 2 little ones are completely connected (both pressure and vacuum) and it seems the big vent would never be utilized?  I tried inserting the piece with the throttle body vacuum line connected to the end of the big vent, and one of the little ones going to the trans.  That way vacuum is sucked from the trans but boost pressure does not go IN to the trans.  However road testing, it didnt make much of a difference?  I bought a new of these plastic vacuum T check-valve piece (got a part number on here a while ago, they said it was for an A/C check vent on a Grand Prix but same part as the trans one).  Blowing thru the 2 with my mouth, they both act the same.  How can I verify whether or not my tranny is seeing proper vacuum?  Even drastic changes like I described, dont seem to have much effect on how the tranny runs.

I also tried adjusting the TV cable.  I pressed the button down and pulled the cable, and then had someone floor the gas.  The cable ratcheted loudly about 8 times.  It seemed to really ratchet quite far.  I road tested it and it doesnt seem any different.  My tranny not only shifts too late at WOT but it seems to kick-down far too easily.  Just breathe on the gas or go up a slight hill and it's going to downshift.  Suggestions??

I will mention this, I had the tranny fluid changed when I got the car and I maintain things properly (cant vouch for whether the prior owner did or not.)  When the tranny does shift, it is very hard and firm like it wants to bark the tires, so I assume my trans is still good, but this TV or vacuum issue is holding it back.  At part throttle going up a HWY on-ramp, it shifts 2-3 hard enough that the dash plastic will creak, almost every time.  Is that supposed to happen?  Finally when I am in boost in 1st or 2nd gear and I let off the gas, the car will jerk like it's doing heavy engine-braking of some sort.  It feels very unnatural.   Is that the closed-throttle boost-wave hitting my transmission?  It seems to still do this even when I changed the orientation of that check-valve so boost theoretically won't hit my transmission?  However if I am in 3rd gear now and I let off the gas under boost, it is smooth as can be.  Hopefully someone can help.  Thanks.

PS: How would my transmission act if no vacuum or too low of vacuum was reaching it?  It is possible I have a vacuum leak, I did not replace the hoses yet (although one of them is metal which would be hard to replace.)