mess up, just about anything. How did you select this shop? What warranty did they give you? Did they just replace 1 injector? Did they pull the plenum to do it? Do you realize your year car has the old style injectors that are prone to failing, some believe due to ethenol corrosion in the electric part of the injector?
All I can add is the shop needs to fess up to fix what they messed up and next time do more research to find a mechanic that knows these cars.