Hey guys Im new at this whole thing so if these are dumb questions I apoligize. I just bought an 07 2500 duramax crew cab 4x4 and i had a few questions about it. First of all, warming up your car, now i live in california so its not to cold here in the morning, never below 40 or so, should i let the car warm up at all or just start it and drive, i know your supposed to take it easy the first couple of miles but what else do i need to know. Also when i shut it off i have heard to let it idle for about 30 seconds to cool down the turbo but then i hear idling is bad???also does 12mpg sound normal as an average with half being highway and other half just showing off around town? One more question, i want to get an exhaust but ive heard that taking the cat off voids warranty so i was just going to do cat back, does it still sound good and add some more power, what do you think? and does anyone else feel a vibration in the brake pedal from the engine when idling??? thanks for the input!