what is aEFE thermal vacuum valve and what does it look like?

Answer 1

The vacuum valve itself will be screwed into a coolant passage, normally at the front of the manifold, and will be 1-2 inches tall with 2 - 4 hoses attached to it. It provides a signal to the Early Fuel Evaporation valve, located on the end of the passenger side exhaust manifold. It aids in reducing emissions and helps the vehicle warm-up faster.

Answer 2

its located were the exhaust manifold and exhaust pipe connect. Its round and has a one vacuum port.