Checking the warm up regulator......

I'm suspecting that the WUR on my 1988 mondial 3.2 needs to be checked. The car stumbles when cold....feels like too lean of a mixture...then run great once the car is warmed up.

For the first couple seconds upon initial cold start up the engine seems to run well, but then the stumbling begins until she is up to temp. I'm guessing here, but isn't there an enrichment device for the first couple seconds of cold start? In any case, until she's up to temp she runs poorly. If she ran bad when warm then I would start thinking about a vac leak or bad cap/rotor and such, but she runs great when warm.

I don't have pressure gauges and such to test the cold/warm fuel pressure myself so I would be happy to send out the WUR for testing and/or rebuilding. Where is the best place to get this done?

Also, on a related note, where does the WUR/ecu get the signal from which tells it the temp of the engine? Is that one of the sensors that's buried under the inlet manifold? Do these temp sensors go bad sometimes?

Thank you in advance.