My '99 S70's engine stutters a bit just as I am about to stop (at a stop sign or stop light). The engine runs fine otherwise. It seems, as the transmission gears down to first gear (around 750 rpms), the engine gags a bit and sound/feels like it's going to give out.
I use 89-93 octane fuel. Any solutions?

Guess what? I've had my '99 S70 in for a week at Volvo. I have the same problem, only the car would stall and shut off.The arrow light would come on and sometimes the battery. Yet the radio and lights would stay on. Volvo can't figure out what the problem is because it doesn't happen to them! They've driven the car for three days and nothing! I just picked it up today and we're at a wait and see stage. I posted it a couple of days ago here, check the responses. I have 49,000 miles on it!

This sounds a bit like the "skip and dip" problem.
But, I thought it affected 98s. In any case, found this
older post that includes the serial numbers of cars
that had the skip and dip problem:

http://www.brickboard.com/AWD/index.htm?id=162340

If your car is in the range of serial numbers then a
Volvo dealer can update your ECU programming. As I recall
it affected the GLT models (LPT engine with automatic
transmission).