Oh Yes. Vacuum problems for sure. The "economy" needle should be pegged to the left at idle. That gauge reads nothing but vacuum. Look at all your underhood lines first. The issue is usually rotted soft rubber vacuum connectors. The first place I would look is the hardest to see and one that is often overlooked for that reason.

Look between the rear of the intake manifold and the firewall. May have to remove the air cleaner (don't remember if you have to). Use a flashlight. You will find a right angle soft connector that attaches to a vacuum spigot on the intake manifold and a hard vac line that runs along the top of the firewall to a 4-way rubber connector on the driver side. One of the lines coming out of that 4-way goes to your economy gauge.

In my case the right angle connector was rotted to pieces. It resides in a area of max oil vapors and high heat and is the most vulnerable of all the connectors because of that. You need little hands and a lot of patience to service that thing as you will see. I used a piece of thick wall plastic tubing as a temporary fix until I got the proper connector.

Check all of the vacuum connections you can find of course. You can buy them all for chump change but my bet is on the one that I described.

Let us know what you find out so we can add to the data base. Happy Hunting.