I'm sure I'm not the only one with this, but get your HHR to about 50MPH and roll ONE rear window down and see how long you can take it. The service writer at the dealership lasted about 15 seconds. Is there a fix for this?

 

dont buy a wagon, pretty much every van/wagon will do it unless you can vent the back windows, put a front one or both back onesdown a bit will allieviate some of it, but not all, just dont drive with one back window down, put both donw a bit.....the air just needs someplace to go, my maxx does it was well, not as bad as teh HHR tho, I chalk that up to the flat vx angled rear window

 

Some of the window visors should eliminate it also, if you can stand the look of them.