Transmission Shifting Late

I have a '97 Town & Country with a four-speed A604 41TE transmission.
The transmission works fine, except that it shifts too late when
accelerating normally from a stop--that is it winds out too far in one
gear, before shifting to the next higher gear. Also when you are at a
cruising speed and give it some gas to pass or climb a hill, it
downshifts to the lower gear much too soon. I'm told that there is
some kind of adjustment to a throttle position sensor that will
correct this problem. Is this true, and if so where and how? Thanks.

-David Kasper