The OEM all metal (cad or yellow zinc plated) valve was discontinued in 2014 or early 2015. There was enough inventory available that anyone who wanted one could buy as many as wanted pretty inexpensively up until the past year or so.
I've noticed in the past year or so that the available supply from Amazon and the Buick vendors has nearly dried up. So much so that partsplace Jo has them on ebay for $300 each.
even a crappy looking, rusted but functional (for now) control valve has an asking price of $100.
So, I thought I'd share that there is an excellent alternative if you don't...