Check the plug on the MAS and the wires going to it. Maybe there's a frayed one. If not, Try to find someone nearby that you could swap one with for a few minutes to see if that's the issue.
What other symptoms are you having? If you want to see if you're running lean, pull the spark plugs and see what color they are. Better yet, pull them and post pics for us to diagnose. Also, make sure the plug for the MAS is all the way on.
Change your plugs, post pics of the old ones for us.
Check the plug on the MAS.
Disconnect negative battery for about 10 minutes and then put back on.
Drive it.
See if light comes back on.