Mass Air Flow Sensor Problem

I have been getting PO101 trouble code which illuminates the MIL. I have replaced the senor twice with no solution to the problem. Sometimes on start up, the cold engine will not race, sometimes at idle in gear the rpm's are about 200 rpm's higher than they should be. The MIL may not be on at this point but I know that sooner or later it will. The engine has been "smoked" and no vacuum leaks have been found. There are no real driveablility issues. When I clear the code, the idle in gear and in park is normal for a short time and then the code returns. I will check the intake snorkel and PVC next. The enhanced Cadillac code says voltage out of range. Do you have any other suggestions on what to check? I am totally frustrated and nobody seems to have an answer. I hope you guys do!

Thanks for your help!