Here's an explanation in a post many years ago from a member no longer active:
".. That's a dampened vacuum source for the Fuel Pressure Regulator. IIRC on the double port 'gas filter' on the AFM trucks, it also feeds vacuum to the PAIR valve...
For several reasons:
1. The 1FZ is a slow, underpowered, old engine and I don’t want to waste money on fixing up an engine that will stay slow and underpowered. For less money I can rebuild my 2UZ to make it fresh and have a way better platform...