So I've been having this issue for a while and recently have started to investigate it. For some reason my idle holds at 1500rpm until I come to a dead stop. I did some research and found out that some cars came with deceleration valves that would purposely do this to prevent a rich condition which could foul catalytic converters. I talked with EuroCharged and Jerry is unaware how to bypass this feature in our cars since we have electronic throttles. I've checked every vacuum line and every connection is held down with ring clamps and still not resolved.

This only happens when the car is warmed up, I also have cat codes P0422 and P0432 so it could be possible that the idle is holding because it's trying to get the cats up to temp.

If the cat codes are possibly the cause for this then I'll probably have to get those replaced even though I don't have emissions testing here.