I'm wondering if your battery is bad causing the charging system to go full bore. From other posts in this forum low voltage/bad connections make this car do some crazy things.
Yes you will get a cel from the downpipe because it doesn't have a cat. Clearance is fine by the mufflers I have not bottomed out on anything myself. With resonators in there is no drone.
I wish the car used just dtm in that style connector. They are used heavily on cat equipment and can take water cannons at full flow and pressure without letting water get onto the pins and sockets.