1993 Pontiac Bonneville RPM

I recently bought a used '93 Pontiac Bonneville SE. When I had bought the car it ran well. Near perfect aside from changing the oil for cold weather. Well my problem is it seems that now that the weather here in Indiana has dropped to about 20 degrees my car has seemed to developed a fun problem where it idles high. If it's in park the RPM will be anywhere between 2-3 when you shift it into gear it goes down but not all the way down it stay between 1-2 and pushes the car by itself. I could be at a dead stop on the brakes, let go and then it'll speed up slowly but steadly to around 35. I'd say that's an issues. It's running the engine hard and not very safe on ice, when I have to practically ride the brakes. I replaced the Mass Airflow sensor and the vacume hoses around it. It went back to normal and stayed perfect until a day when I actually had to hit the gas and "get out of the way" it returned to the issues. I'm wondering if there is anything else I can do or if it's just one of those things where it's going to act up in this kind of cold weather and just need to be careful. I'm used to older cars so I know sometimes it's just something you deal with in such cold weather. Although If I can fix it I'd like to. Any suggestions?