1999 Mazda Millenia S 6 Cyl 2.5L
low speed hesitation with some vibration while stopped
speed above 40 mph car runs fine. Plugs have been changed and cleaner has been used inside of the intake which also helps for awhile.
It is possible that EGR is faulty; it is not opening when you are decelerating. Possible also that throttle position sensor is failing. But clean the air filter first and replace fuel filter. Have your PCM scanned for stored trouble codes to verify these.