I noticed this too. I’m assuming that the resting position for the baffles in the exhaust are normally open (loud mode). When we start up cold the Engine Control will richen the mixture and increase RPM for quicker start and warm up. (Engine has to be in Closed Loop fuel control within 90 sec per law). I think the rich mixture start with baffles open (they close in a couple seconds), causes the pop/explosion which does a great job a rattling my neighbors windows. (Heh, heh...)Keep in mind that I'm a new owner with only 400 miles in the seat, but I just noticed something yesterday that was interesting to me..
You know when you first start the car up cold there is an explosion, all 4 exhaust valves open, then it closes 2 going into normal mode.
Yesterday I noticed starting up the car (when it was already warmed up) that it was not the same explosive sound, obviously only 2 exhaust valves open.
Anyone know the mechanical reasons behind this?
BTW- what part of San Diego? My brother is in Ocean Beach...