tstad, mine was going back and forth for awhile. On a freeway off-ramp I take every day, I do a double-clutch downshift for the Heck of it. Rev-matching from ~2200rpm to 3200rpm sometimes took me flooring the pedal for 2-3 seconds! THAT'S lag! Other times I'd just touch the pedal and it would immediately hit 4500rpm, more often after a large pickup truck rear-ended me. I figured something had been jolted loose.
I cleaned out my air intake piping from the inlet under the hood to the airbox. The slush screen was almost completely jammed, so I removed it. The problem hasn't reoccured since.