Michele....give the suggestion about the carb cleaner or similar aerosol a try....I got some feedback some another forum and everything points to a leaky intake problem or EGR valve sticking or leaking....
New gaskets can be installed and leak!!!!! If NO change in RPM with the spray...then you can surely say it is not a intake gasket issue....

Becareful not to spray on the exhaust system...the spray is flammable and dangerous!!!!