2003 Mazda 6 Engine Idle

I have a 2003 Mazda 6 with approximately 130,000 miles on it. When I start it up first thing in the morning, I need to let it sit for about 4-5 minutes until the idle comes down to about 1,000 rpm. If I end up putting the car in drive/reverse right away and not letting it idle down, the car will continue to idle high as I drive or when I'm sitting at the stop light. It will even push the car forward when breaking, causing me to really step down on the brake. I have also found that if I don't let the car idle down when starting, that the next time I start it, it will blow white smoke out of the exhaust in an exessive amount. I've recently had a tune-up and they found nothing wrong with the engine, so now I'm looking to you guys for help!