Engine Performance problem
1991 Audi 100 4 cyl Front Wheel Drive Automatic 50,000 miles

Recently, the pump that supplies fluid to the brakes and the power steering went out and was replaced.
Since then, the brakes have felt hard though the the pads and rotors show no signs of wear and the fluid reservoirs remain full.
The real problem is that all of a sudden the engine started sputtering at low revs. It sounds like it's going to stall at idle and it is difficult to get going from a full stop. Once the car is moving, the engine sounds perfectly normal.

Any thoughts?
Yes, 50,000 miles.