9-3 power steering pump on a NG900?

[AmuseMe]

Hi guys, new member here

I own a 1997 900S. She's quite literally a pain in my backside and bank account, but just the thought of getting rid of her makes my heart ache. So, here I am presented with a problem.

A couple of months back, I was driving the car down the highway when the belt tensioners snapped and the belt went byebye and my power steering pump was damaged in the process. My mechanic at the time was forced to replace it with a pump from a 9-3 because in all honesty, getting parts for the 900 here in Cyprus is a nightmare.

Ever since then, she's been going through petrol like pizza and the engine sounds rough, fully loaded and vibrates much more than the norm. I've replaced the Mass air flow sensor and the air intake temperature sensor but nada. The only thing I can think of (because everything else has been checked) is the 9-3 power steering pump because it's the only thing on the car that doesn't belong. Could it be that it's making the engine work harder because it's all on one belt system? Any ideas? I'm at a loss!

I've tried researching this problem but couldn't find anything and I have looked in this forum for anyone with a similar issue. If there is a similar thread, I'd love the link to it. Thanks!