Well if it has anything to do with what you did then you have a mixture problem of some sort. could be false air (vac leak), could be the airflap is binding or it could be just not adjusted properly.

Properly should be done electronically and is simple but has been explained ad finitum. To determine what you have and get close try having someone start the car and hold it at 1000rpms (where it runs). Place a finger on the airflap and gradually let up on the throttle. As the engine slows and approaches dieing press gently on the airflap. If it makes it run better the engine is lean for one reason or another. Let the throttle all the way off. add pressure to the plate till the engine runs strongest. If the engine speed is above normal idle when doing this then you have an air leak (uncontroilled air).

If pushing down the plate causes the engine to stall quicker then you are already too rich. If that is the case back off the mixture with the 3mm mixture screw in the tower. If the engine ran good pushing the flap and ran at normal idle speed turn the mixture screw in till the motor runs good without pushing the flap. This only gets you a crude set-up the final adjustment needs to be done electrically which is simple read my article in DIY or others to achieve the total adjustment.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician