OK, that helps. P1251 is a throttle body error code. When the fault is present, its causing the car to not start correctly (which is why you need to give it a little gas to get it going).
When I see this code, the throttle body is usually in "limp home" mode. I reset it and clear the fault codes, but it usually comes back anyway and getting a throttle body. This part is a little pricey, which is why I always try resetting it before selling it.
Resetting it is a little tricky to do, especially if you are not familiar with the throttle body or the procedure, so I would reccomend finding a Saab dealer, or a Saab specialty shop in your area. Most people don't like going to the dealer, which is understandable, so you can visit www.saabshops.com and locate an independant shop that specializes in Saabs to took at it for you.
Wether the throttle gets reset or replaced, the codes MUST be cleared BEFORE the repair and must stay cleared, otherwise the next key cycle will put it right back in Limp Home Mode.
If you have any additional questions, please feel free to ask, I will be happy to helps.
These procedures should really be done by a person familiar with Saab vehicles, but if you want to give it a try, here is the procedure to replace (towards the end of the article shows about resetting limp home mode if your not replacing it).
Please note this procedure is for a 4-cylinder, but your 6 cylinder will be similar.
You need a scantool or at least an OBD II code reader to clear codes and know if they have been cleared.