1990 Suburban high idle/whistle from IAC

[SoCalSlaughter]

I've used a vacuum pump to confirm the EGR valve is holding vacuum which it does. I've replaced the EGR base gasket. Could the EGR not be closing all the way cause a vacuum leak? Also an update, yesterday I was driving the truck around, got off of the free way and just before I came to the stop light, the truck surged and the engine light came on for the O2 sesnor saying "Lean". The engine idle was at 1200, and after sitting at the light for a minute the whistle went away, the rpm dropped and the light turned off. The truck just went back to normal running condition. I'm lost. haha