Your SAAB is in “limp home mode”, which is why the power is down and it’s running sluggish. There is a spring on the throttle body that can be reset to put the car back into “normal” mode. However, something else (direct ignition cartridge, crank sensor etc.) is causing a misfire and putting the car into limp home mode. Unfortunately, this means that you probably did not need the new throttle body (ouch!). Classic case of throwing parts at a problem without doing proper diagnostics. I’d go back to the shop and have them look a bit further - and give you a credit for the $900 they charged you for the throttle body :). Good luck!