Hesitatoin or pulsating while pressing the gas pedal

Hello, it's very hard to know for sure based on your description, but in some ways, it sounds like a slipping from the transmission. In a higher gear like 3rd or 4th, you could have an engagement issue causing a lack of proper acceleration and shuddering. As always, hands on road testing by a trusted technician is the best idea to give you the best advice, and usually a road test can happen before a charged diagnostic test. Worth a try.