There are lots of different reports about A/C impact on MPH and acceleration/power. And, I agree with the previous poster that A/C will always have some effect. But your experience seems to be extreme, which may mean that something is not quite right. I don't have it in mine, but my daughter has a 2006 with A/C, and I will be visiting her over Thanksgiving. You've made me curious about this, so I'm going to check to see what the difference is on her's. I'll probably be the only person north of Arizona running the A/C