1992 t-bird w/ high idle

after 3 years i finally got around to putting new rear end gears in it. it stated up and now it has a high idle. so going down the road it does a steady 20 by itself. no codes yet since the battery just got put back it, but are there anythings to look at that could cause this?
thanks

thanks for ALL the help......
figured it out myself no thanks to your all great help :mad:

Cool glad you got it figured out, can you tell us what it was?? I have the same problem and would like some ideas, Thanks,