A few days ago, I was sitting idle at a red light when I fell a slight bump. It felt like a misfire that made the car feel like a bump. A couple days later, I felt it again while at idle waiting at a red light. Now, I started paying more attention.

When I feel the bump, which feels like a misfire, the idle drops one notch on tachometer momentarily then recovers.

Also, if I'm in reverse, stop, then switch to drive, idle drops approximately two notches on tachometer, then recovers?

Any thoughts?

On the squeal, it's intermittent. Not like a belt squeal, but almost like a dry, no oil engine squeal. I checked my oil level and there is plenty of oil. Oil was changed just 1k miles ago and still looks fairly fresh on the dipstick, nothing out of the ordinary. The squeal comes and goes, but only have heard it while at idle. I've read across a few posts about a squeal that's caused at the connection of exhaust to catalytic. Was this issue an intermittent noise type or constant?