I have an audi a6 2004 s-line quattro. When the vehicle is off and parked, and when temperatures rise, the brake lights will turn on and remain on until temperatures subside. Also, when first driving the car during the high heat, even though my foot remains on the gas pedal, the car will stop accelerating as though I had taken my foot off the gas. Despite pressing down even to the floor, the car will continue to not respond to the pedal until I have let the pedal return to it’s unppressed state, at which point it will respond once again to the pedal. This behavior will continue only for a few minutes after the car was started during high temperares. One other possibly related thing is that my gas tank is leaking, but only if it is filled beyond the halfway mark.
Help, please…what are the likely causes, can I fix them myself, and if not, does any one want an audi a6 2004 s-line quattro…it has a clean carfax and absolutely no problems…whatsoever 
Thanks,
Andrew
Brake lights- check the adjustment of the brake light switch
Accelerator- possible throttle position sensor
Fuel leak- just have to find the leak and fix it