Pontiac Repair: air flow through vents (air conditioning vents, floor vents, etc.), pontiac grand prix, pontiac grand prix gt

Question
After traveling for a while at sustained highway speeds, the air flow, whether through the air conditioning vents or floor, whether cooling or heating.... stops.  You can still here the fan running.  But is sounds as if a louver or some kind of door has closed in the duct system.  The fan noise gets much louder when this happens sounding as if the air flow has no where to go.  Get's fairly loud under the dash board.  If you come to a stop and sit for a several minutes, the air flow starts to come out once again.  You can tell when it starts to work normally again because the loud, blocked air flow sound starts to diminish and air flow comes out like it should from the air vents.  Once you start running at sustained highway speeds again, after 10 to 15 minutes, the air flow will again start to be restricted, falling off to barley a noticeable trickle.  This is a 2007 Pontiac Grand Prix GT with just 14,000 miles.  It was doing this since 7,000 or 8,000 miles.  Took it into the dealership.  They really didn't have a clue.

Answer
Hi George.
I do not want to slam any fellow mechanics, but if you can make the car act up regularly, I would take it back to the dealership and DEMAND the car fixed. With that few miles on it, and with ALL the help GM supplies the dealers, there is NO REASON why they "Should not have a clue".
Have them look at this Document ID# 1459206  in SI2000.
Have them preform the function test. Have them check for HVAC codes.
If all else fails, drive with them UNTIL it acts up.
This is what I would recommend.
If all else fails either
1) take it to another dealership.
2) when you recieve the Customer Satisfaction paper fill it out Unsatisfied. That'll probabally hit them in the pocketbook.
3) call the GM number and tell someone higher up.
You shauld not have to spend ANY MONEY on this car except maintance.
Good Luck
Just advice from experience.
Pawl