1994 Ford Explorer 4x4 A/T Transmission Vacuum modulator trouble

What is your question?

I just replaced my old vacuum modulator because it was leaking transmission fluid into the vacuum lines, after i replaced the modulator it doesnt shift like it should, it'll shift from 1st-2nd and then at around 20 MPH in 2nd gear it'll downshift back into first instead of third. Anybody know how much it would cost just to have a mechanic look at it? Because the modulator i installed is a ford part and it is adjustable.