It could be a air leak in the manifold or the throttle body. It would explain the bad cold start and also the lost of response (and power).

'cause if there is an air leak, than air will enter the engine via that leak source instead of passing by the Air flow meter plate (AFM), and the AFM is directly responsable of the quantity of fuel injected (with the fuel distributor). That would also mean that you have the incorect fuel mixture = lack of power. Check for air leaks if the cold start injector isnt the problem, and also check your lamda value with the duty cylce to be sure that you have the correct fuel/air mixture.

Good luck!