92 Olds 98 strange problem...

Hey everyone,
I have a 1992 Olds 98 Regency with 298K on it that just won't die! I love this old car and it still rides like new.
However, the old girl has developed a strange habit at idle.
The idle speed continuously fluctuates while the car is stopped. It revs up and down, up and down, up and down, every 3-5 seconds. Often it revs down enough that the engine almost stalls out.
What is up with this? This car since 90K miles has flashed the usual CES light every now and then (especially when cold) but it is the EGR code (nothing has ever gotten the ECM to forget about it) but there are no codes other than that.
Anyone have a suggestion as to what is going on (and hopefully a cheap suggestion) with this old gal?
Thanks in advance, BigBob
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BigBob wrote:

Possible vacuum leak. Do the usual: clean, test or replace: throttle body IAC EGR MAF TPS
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