rough start and shut off
 

I just purchased a 1999 XC AWD with 137,000 miles (EBAY) I drove 1700 mi. to get it. It has a rough start and shut off. I encouraged my sister to buy a 1997 Saab 900 SE a year ago and hers does the same thing. Is this a Turbo characteristic? I've never owned a turbo. My sister saab has driven fine, and my volvo as well. I have a check engine light on telling me ERROR pedal position sensor, ERROR emmissions system leak. Could this be the problem. Also a lovely ticking noise is coming from the engine, could this possibly mean that I need a valve job now? I love my first Volvo. Had a Jaguar once so I'm not scared yet. Any response would be greatly appreciated.