[ground-pounder]

Has anybody experienced this: I made a plate with a 5/16 hole in it, installed and checked for leak with carb spray, so far so good. Idles fine even with a/c on, and rpm's definetly come down quicker, now here's my problem, after I drive for a while when I go to stop,as I push in the clutch to start slowing down and my car revs to about 2000 or so all by itself and then dies. It does this every time after my car worms up, I can take the plate out and it's fine, I put the plate back in, same problem?? Thanx for the help