Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Do you mean vacuum problem with the engine?
What is your concern with the car?
I would perform a compression test and a cylinder leakage test.
I could be possible that the valves have carboned up, quite common, and you have weeping valves, which gives low vacuum.
What symptoms do you have, low power, hard starting etc?
How many miles has the engine done?
I would suggest you give the engine a dose of "upper engine cleaner".
Have done this many times, fixes a high percentage.
Gets done on every service for Subarus, they know about carbon buildup.