Brian Dud

I have a 2013 GTS with about 55k miles. The engine RPM seem to pulse 50 - 100 RPM. For example, while cruising at 73 mph, you can watch the RPM needle pulse from about 1900 RPM to 2000 RPM. It does it at all speeds to some degree. Sometimes 25 - 50 RPM, sometimes 50-100 RPM. But speeds like 73 MPH and 78 MPH are more obvious, because it is easier to hear the sound of the engine change with the sport exhaust. It's been pretty consistent the last 3000 miles or so. No check engine light. I had it at the dealer for a shaking issue, that I thought may have been related. The shaking was corrected but the pulsing continues.

Any thoughts?