Took my '01 s60 in for a timing belt, and found that, since two weeks ago when I brought it in to have the throttle wire looked at, Volvo put a recall out for a new software flash. Hopefully this will help, as I've continued to experience degradation of the throttle control - occasional sluggish response and mild self-revving. The first major occurrence, which invoked limp-home status, wrote no error codes in the computer, so I doubt these relatively minor events did either.
I remain impressed with the service dept at Mid-Hudson Volvo in NY. They did the timing belt job on the low end of their estimated range, and had given me a 10%-off coupon as well.
They also gave me an '06 s40 to drive around. Quite a peppy little car. The dashboard electronics have progressed nicely. A bit small for me, but it made me realize my s60 is a little tired now at 104K.
Paul