I have developed a vacuum problem. I have a 3.8 turbo engine. I have had some issues with my vents changing from floor to dash vents. Last winter I changed my rearend gear ratio to 3:42. The vents change ok at idle or low rpm. When I am going above 60 mph I am not running very much vacuum, under 10 psi. Do to the higher rpm and turbo. My vents switch back to the floor. Do I need a check valve on my round ball or is this the nature of the beast? The car does not get drivin in cold. Is there a good way to lock it in dash vent position? What are your thoughts on this problem?