My manifold upgrade project is coming along well.
All vacuum plumbing issues are resolved, thanks in large part to the help I received here in HiPo.

This should be easy - someone tell me the purpose or function of the sending unit in the picture. I believe that oil pressure is the canister next to the distributor, and coolant temp is near the thermostat, so what is this one?
Elementary, I know, but I drew a blank today.

Thanks in advance; enjoy the picture of the engine bay in progress.
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