1999 BMW 750il with a 5.4 12 cylinder 85,000 miles. I did a tune up on it and now after the vehicle warms up it's making an ungodly howling noise down by the torque converter area. But when you let the motor cool down and start it back up it goes away until it warms up again. What can this be? Is it something I did or pure coincidence?
Could be the PCV valves on the back end of the plenum (one on each side) it would make a sound like you described. To check this use a slack tube manometer at the crankcase, more than 6" of difference from side to side and that's where to start. Re post if more help is needed.