Well yesterday I swapped out a set of longtubes for some short tube headers, and in the process banged up some spark plugs. So when I drove the car it had a miss during acceleration. I swapped out the old motorcraft spark plugs for a new set of E3's. Before the spark plug swap my car idled around 550 rpms and was kinda rough. Now when I am driving and push in the clutch to come to a stop the rpms drop slowly to around 1000 rpms, and after letting it sit for about 15 seconds longer it will slowly settle down to about 800 rpms(right where I want it). Is this a problem or is it okay to have an idle that high?