Must have found a rare time when the 405 wasn't jammed to start doing that :nice:. I also live in the wonderful San Fernando Valley area. Nice to hear a happy ending to the story.
I was having the same problem for awhile too. I took it into the dealer and they said they knew nothing about it. It has been better, partially because I have avoided the stations that were primarily causing the problem (Valero).
I have a 2007 GT with the 5 speed and 26,500 miles.
I average about 18 mpg in mixed conditions about 50/50 highway and street.
Only mod I have on the car is the Flowmaster American Thunder Exhaust