1993 3.4 idles at 1500-2000k?????

[white96six]

ok my wifes 1993 3.4 all of a sudden started idleing at 1500- 2000k. I have checked all of the vacuum lines and found no problem. i pulled the IAC motor and cleaned it and i was told when you do this to push the valve all the way down before reinsalling it but and have done it on other cars before but this one would not push down. do you think that means that it is broke? also how do i check to see if the power booster is the prolem? when I push on the brake and then let off the idle raises another 300 rpm the coes back to around 1800. any help would be great thanks.