either the idle is set too high or you have a vaccuum leak. There's a flathead screw you can adjust near the intake hose, I think. I haven't had a DC4 in months so I forget if that fixes the problem exactly, lol.
i found the screw.
it was turned all the way up.
i turned it all the way down it helped a little it brought it down to 1200.
so like you said its probably a vacuum leak.
how can i find it?
ha yeah when i cold start it goes to 1500 hundred then slowly up to 2k them slowly back down as it heats up. After i've drove a bit and go park somewhere and come back like 5 minutes later and start my car. It idles at like 400 to 800 man lol.