1994 Chevy Cavalier Starting and Idle Problems

Hello,
1994 Chevrolet Cavalier 3.1 Automatic. I just replaced the starter and another problem has appeared. When I start the vehicle, the RPMs go up to about 2000 for about 5 seconds and then settle down into a normal range of about 7-900.

It also has an intermittent problem when driving, while both warm and cold the idle will sometimes drop from normal to about 300 and almost die then rise back to a normal idle. It will rise and fall until the gas pedal is pressed and then the car will drive normally. Once in awhile it does actually stall, usuall when on a hill or backing in reverse. I've noticed the transmission downshifting a bit rough recently so I'm wondering if it could be something related to that. Thank you for any input you may provide.