This is an '04 XC70 with 120K miles, well-maintained. B5254T2 engine built for CA/USA.

Recently, while driving on the freeway, I noticed that when I step on the gas above 60 mph, the car lurches.
It feels like an instantaneous "kick" forward, then recoil back, each kick over with in 1/3 sec. It feels like there is an instantaneous bump in engine power (acceleration) followed immediately by a decelleration. It only happens above a certain amount of acceleration. If I switch on cruise control, and tap the "+" switch to speed up, the acceleration is very slight, and there is no kick. If I floor the gas pedal, the tranny responds properly with a kickdown into 4th. I can slowly accelerate from 60 - 80 mph using the gas pedal with no kick.

I studied and graphed some ECM parameters using my OBD-II scanner. The results shed more light on this completely repeatable engine fault that leaves no codes:

http://www.volvoxc.com/forums/showthread.php?45081-Throttle-quot-kick-quot-during-accelerations-over-50-mph

Any thoughts on how to diagnose this problem?