Are you getting any engine codes?

The M119 has an electromagnetic camshaft advancer - they adjust around 3000 rpm to deliver extra power (On my E420 it feels like a turbo coming on at 3000 rpm). There are wires that attach to one on each cam bank. I would say that perhaps a connection has come loose on the passenger bank, but this would probably trip a Check Engine light.

The Throttle Actuator is a much more common problem (I've never heard of a camshaft advancer problem on this board). And at 140k miles, much more likely if it's never been replaced before.

For your sake I hope it's not the actuator - I think they run around $1000 just for the part.