why won't gm back up their vent valve defect? My tahoe is under 2 years old and I have to have that thing replaced about as often as I have the oil changed. They are telling me I need to put a $600 "kit" in and have the valve relocated to under my hood. Why won't GM take care of this?! IT's their fault it's like this- not mine. I hear most all GM vehicles are like this too. Is GM so ignorant to only build vehicles assuming they will only be driven on pavement and no gravel/dirt roads on a regular basis? VERY frustrating to spend $40,000 on a vehicle then to be told we need to spend another $600 less than 2 yrs later!