"I had a noticeable shudder while accelerating occasionally, and also a noticeable 'stepping' up in RPM's as I was accelerating (RPM's would jump up 200-300, then stop, then jump up 200-300, then stop, etc...)"

Shit, mine started doing this a few weeks ago at 131K. The shudder is rare but it's there and I constantly notice the RPM step-up between 1,600-1,900RPM on light throttle.

Great. I have zero trouble codes as well.