There are T-shaped vacuum connectors under the intake manifold that can break and cause a rough idle.Google+
Car Problem Reports
Mazda Millenia Rough Idle Due to Broken Vacuum Tee
Mazda Millenia Problem
Engines Affected: 2.3L V6 Supercharged, 2.5L V6
Average Mileage: 150,333 mi (130,000 mi - 177,000 mi)
Visitor, 2001 Mazda Millenia, 2.5L V6, 177,000 mi
mechanic damaged the intake which have a vaccum leak. need to know how to repaired the vaccum leak and the cost of repair.
Car was in for service and the next day it began to idle rough. I brought it back into the shop and they identified that the t valve had become cracked and was causing a vacuum leak. The mechanics denied any wrongdoing and so I took the car to another shop to repair the issue. Not saying that they broke it but their ice cold bedside manner didn't provide enough reassurance for me to keep shelling out perfectly good benjamins to suspect mechanics.
the dealer found the problem. Have not been fixed yet. Looking to find the tee connector at local auto parts store.