Ok folks. Got a question. My 86 SS runs really well but i have a concern. When i fire her up cold the choke comes on as it should. After a couple minutes of running it comes down depending on outside temp. Yesterday i took her for a spin. At first it would idle at 700 or so rpm. But after a half hour or so of driving i noticed at idle it was around 1100. And it wouldnt come off that. It ran great. Just a high idle. Why would it be fine for the 1st say 1/2 hour of driving and then all of a sudden jump up to 1100? I have changed all the vac hoses and the AC was not on.