Engine Hunting Problems on Volvo 850

The engine on my 1993 2.0L Volvo 850 has recently started "hunting"

When the car is stationary, the engine revs are not at a constant, steady rate - it tends to decrease and then pick up again. I have also noticed that the car does not seem to pull away (i.e. accelerate)quite as fast as it used to

I have just taken the car to the garage and they seem to think that it is a problem with the power steering pump and quoted £350 to replace it.

Now......I am no mechanic, but I just can't see how the power steering pump can effect the engine in this manner. Yes, the problem does seem to be more pronnounced when you turn the steering wheel (when stationary), but surely a power steering pump issue wouldn't affect the engine tone when the car is left completely alone ?

Thoughts/comments anyone ?

Thanks

Mike

[sholtby]

Prabably a vacume leak. Check all your pipes for splits/damage.

Simon