2008 Toyota Yaris Engine pulsing sound over 55mph

I just purchased a 2008 Toyota Yaris. The car is excellent with only one exception. When above 55mph, I hear a pulsing noise - a constant evenly spaced noise similar to an engine that is lightly revving on and off. If I take my foot off the gas, it goes away. Press again while I’m above 55mph, and it pulses again. I have no loss of acceleration, no bucking, and the rpm gauge is steady as she goes. It is an automatic. No noises or anything under 55mph. I’m perplexed, and I would love to hear some feedback on the issue. Thanks a bunch!

Without being able to actually listen to the car, have you had the wheels checked for balance and runout (ie bent wheels)? Another potential area is the wheel hub bearing assembly, which may be starting to go by making noise (usually a “helicopter” type thumping). If it is a wheel bearing, I recommend replacing them as a set if funds allow.

Could the pulsing be some kind of “harmonic” distortion set up and wind noise due to airflow? Try cracking each window open a bit (moon roof too if equipped) and see there is any change in the sound.