1990 Chevy Corsica high idle

Engine Performance problem
1990 Chevy Corsica 6 cyl Front Wheel Drive Automatic

I just bought this 90 corsica, it has the 3.1 V6 and three speed auto trans. The previous owner ( not very mechanical) told me he replaced the IAC and the coolant temp sensor. The car refused to idle. I drove it for a week trying to take a best guess at the problem and decied a possible intake gasket problem. While putting the new gaskets on I found that he in fact didn't change the temp sensor but meerly pluged it in and set it next to the old one. I finished installing the temp sensor and presto, now the car idles. Here's my problem, now it idles too high. I thought after it ran for a while it might slow down but it never did. The car will actually pull itself on flat roads at 25 to 30 mph. I'm on a bit of a limited buget and don't want to just start throwing money at the car hoping to heal it. My thoughts were the TPS or 02 sensor. The car isn't giving nor ever did give a check engine light. I'd love a second, more educated, opinion. Thanks, Fred