My 1990 cadillac sedan deville Idles high. on 1990 Cadillac DeVille

If I press on the brake hard it will idle down. When I am driving if I let off the gass it will maintain speed, without the cruise control on. I just had a tune up done and it has been doing sinse then. What could thye problem be?

Asked by for the 1990 Cadillac DeVille
possible vacuum leak