shifting problem when cold..

[96spyderman]

1998 GC L6 TSI AWD
This is the second winter I have had this problem, when accelerating from a stop either easy or hard it shifts from 1st to 2nd just fine, but when going from 2nd to 3rd it just climbs up in rpm's and then will shift much higher than usual. I hear a distinct vaccuum leak from the engine area more from the drivers side. Sometimes when it shifts it has a lag getting from 2nd to 3rd kinda like it is in nuetral. This isn't something just when the tranny is cold.
If I am driving and slow down enough that I go into 1st but don't come to a complete stop and accelerate again, it shifts fine.
Could the vaccuum leak have something to do with the shifting?
Unfortunately transmissions are a weak spot for me..
Oh yeah.. usually only does it when below 30 deg... and the colder it gets the worse it gets.
All fluids are newer.
I have checked all vac lines n such for cracking but everything is in pretty good shape.