I know it sounds like a vacuum problem, but has anyone had this problem? Going from 2nd to 3rd (auto trans), car jumps into gear, then bogs out with a low growl in 3rd unless hard throttle up into 4th. If I'm city driving in 3rd, and just on the gas pedal lightly, it makes this low noise and feels rough at that time. No problem on the highway, throttling up to 5th (getting on the highway), or in 1st. Anybody have any ideas before I go to the dealer?