My Seville has one of the most annoying traits of any Northstar I've ever been in. When you're sitting in traffic, the car has an idle that is anything but perfect. It's a slight "miss" you can only feel through the seat. The tach shows no movement whatsoever, and the car runs like a raped ape. So far, it's the only Northstar (of 20 or so I've driven) that has ever had one this bad. It feels almost like a slight misfire. Shows no codes whatsoever. Brand new intake plenum boot and new CKP. Whats the deal here? Tune-up? Slight vacuum leak? It has done this since I purchased it, and does it when its cold or warm. Temp of the motor has no effect. I thought for sure it was a cracked plenum, but I guess not. It's not a big deal, it's just annoying because otherwise the motor runs beautifully.