I have an '04 S60 R 6spd manual 57,000miles.
Here is the scenario of whats going on...
When the engine is sitting at about 2000rpm and I accelerate heavy, pedal to the floor, or almost to the floor at about 2300 the car shakes and the acceleration stops briefly, it almost feels as if there is a grinding or some gears aren't meshing properly and flowing smoothly, and then it happens again at about 2700, when it happens at 2300rpm its worse than the 2700 but you can definitely feel it at both. The steering wheel, pedals, seats, everything vibrates when it goes through these patches and the car hesitates badly. It does not do it in first or second gears, but third through sixth I accelerate heavy from 2000rpm or below it always happens. If I accelerate slowly or very gradually past the 2 rev points it does not happen. Also if the engine is not engaged(car in neutral) and I just rev the engine it doesn't happen so I know its not engine related. So that leaves turbo, transmission, wheels, AWD system all still possible culprits.
Has anyone experienced this and know what is causing it, and whats taking place that this is happening, and how much $$$ this is gonna run me.
Thanks for your help guys....

 

Has the throttle body been cleaned lately?
Last tune up?

 

I do not know and do not believe the throttle body has been cleaned recently. She just had the PA inspection and emissions inspection.

 

I would try cleaning the throttle body and see if it helps.