Most auto parts stores can check for generic codes with there scan tool and they do it for free. I would start with that and see what codes they come up with. They can scan the car as a Chrysler Crossfire if there tool will work with that, or as most of us do scan the car as a Mercedes 2003 SLK 320. Without a scan and the DTC code ( get the exact code number !!!!, some explanation like you will need a ERG valve is worthless) you really have no idea what is causing the check engine light.

I also will add that what you are experiencing is so very common after picking up a car from a shop that I long ago STOPPED going to auto repair shops and do 99% of repair work myself. I have been burned in my early years by dishonest shops who fix one thing, but deliberately foul-up something else to get return business. Of course the fouled-up is an easy and quick repair (they know exactly where to go) but they will tell you something else and charge much more for the repair. Hope I am wrong, but as I said I have seen this too many times. Good, honest repair shops are hard to find. If you do have a good one, stick with them and pay what they ask, because in the long run you come out ahead. Good Luck.