My wife also has a 2008 GS. She has ridden in parades, stop & go traffic, etc. during 100 degree Texas summers and never had an overheating problem. I think you have something going on. Maybe low coolant, old coolant, empty/cracked reservoir? I can't say what the problem might be, but, although they are helpful, you shouldn't have to add aftermarket parts to fix the problem. Good luck and be safe.