1994 Chevy Blazer Throttle position sensor

My engine has been idling ruff lately and smells rich, and has been revving by itself when I'm sitting at a redlight, so I tested the TPS, which tested bad. When I replaced it, it stopped the revving, but my transmission wouldn't sift right. It would take forever to shift out of first, and when it did, it slammed into second. Also, just changing between park and drive would make the car shutter. So I figured it was a bad part. I took it back, got another one, then tried again. Well, the new part does the same thing. My gear shifting is hard pressed and erratic. When I put the old one back on, my other problems came back, but the transmission shifted fine. What am I doing wrong??
Thanks in advance,
Mark