Mystery Noise - 2018 KTM 150 SX

Hey all, seeking any leads in what a mystery noise could possibly be. Bike is a 2018 150SX setup for off-road. It has 102 hours and I am meticulous on maintenance. The noise is a whirring “turbo” sound that is very audible when idling and lightly blipping the throttle. There is no vibration felt through the bars/pegs and if you ride the bike, all feels normal. it appears to be coming from the clutch side of the motor. I assumed it was a crank bearing starting to go. I tore it down and put new OEM crank bearings. The crank was tight, well lubricated, no play in big end, no play in crank bearings or any apparent issues. I checked all trans bearings while it was apart and all seemed tight and well lubricated. Top end is flawless (has 10 hours on it, I do top end every 30 hours). After reassembling the noise is still present. Pulling in the clutch makes no difference. i have ruled out external vibrations such as pipe, skid plate, etc.