[Jaxonalden]

I was thinking the same thing as Insite, the description you give sounds like a vacuum or intake leak. The engine revs, then it’s compensated by the computer and falls back to idle rpm and the process starts all over again. Get some carb cleaner (with the red spray tube for precise targeting) and spray around all the places aft of the air flow sensor where parts come together. Squirt around the boots and if that doesn't find the culprit check to see that all your vacuum tubes are all connected. Also, look for a crack in the plastic intake plenum.