Low mpg

I have a 1978 toyota pickup with a 20r engine. 83,000 miles. Mechanic says i need to replace the TVSV [thermo vaccum switching valve] to double the gas milage. Where can I get one or is there a substitute for it?

Oh, this vlave sits on the intake manifold and has 3 vac. lines on it.

Why didn’t your mechanic replace it?

Have you tried to find one at your local auto parts store? If not there, the Toyota dealer should be able to get one for you.

What is the mileage now? It’s hard to believe you can double it, no matter what you do, unless you’re only getting 10 mpg now.