1987 S4 Cold Starting Problem -- otherwise runs fine - warm starting fine

Hello,
I have a 1987 S4 that has a hard time starting when cold.  To start it I have to pump the accelerator.  I've had the ECM changed recently.  I replaced the Temp II thermostat (Bosch) and tested its OHM levels which appear to be in spec.  If I disconnect the Temp II thermostat, as suggested in a post I found, the car will start up when cold or when warm.  The car runs fine once its warmed up. 
Any suggestions?
Was it a mistake to get the Bosch part?
Thank you in advance for your suggesstions.

 Cold starting requires air/fuel mixture enrichment ... a bit more fuel since combustion isn't as efficient. 

So, to find the cause of the problem let's look at how the engine manages air/fuel mixture. The mass airflow sensor (MAF) measures the mass of the air “inhaled” thus providing the data needed to calculate the proper amount of fuel to inject.  Engine temperature is reported via the Temp II sensor.  The fuel injection equation relies on a consistent fuel pressure that is maintained by the fuel pressure regulator and dampers. The Temp II sensor can be checked, these are the specifications:



So if there is concerned that the new Temp II sensor isn’t functioning correctly, the resistance can be checked.  The resistance is measured between one of the two connectors and the body of the sensor ... there are two sensors so check each terminal.

Don’t overlook the connections and the circuit between sensor and fuel injection module, check the connectors and the wiring connectivity all the way to the LH connector. Other causes of cold start problems can be a vacuum leak which would overcome the cold fuel mixture enrichment.  So a check for vacuum leaks would be prudent. A less known cause of a lean air fuel mixture is the MAF itself.  Over the decades of use, the MAF output voltage drifts to “lean” … so it improperly reports that more air is entering into the engine so less fuel is injected.  The lambda air/fuel adjustment system can compensate for a lean running condition once the engine is warm as the O2 sensor “reports” the lean burn condition.  However, the Lambda system is only operational when the engine is in “closed loop” mode, when the engine is warm or the throttle is widely opened … at these times the mixture would be overly lean.An original MAF or more than decade old MAF is suspect and the calibration should be measured.  The MAF should be viewed as a maintenance part and be rebuilt as needed.  Through my company, I offer free testing to 928 OC members of the LH fuel injection module and MAF.  Contact me at info@electronikrepair.com if you’d like further assistance.

Hi Rich928,
Thanks for replying and I'll keep you in mind if I have symptoms related to Mass Air Flow problems.
I turned out that it was the sensor.  I reread everything I could and it kept pointing to the sensor.
I ended up buying the part from the Porsche dealership in town.  The car started right up cold or hot and is running smoother.
Sometimes it's the parts.

I'm glad to hear your 928 is now running well.