I bought my 2008 Chevy Aveo used around this time last year and about four months after I bought the car the alternator needed to be replaced. I don't think this problem is occurring with any relation to the alternator, but I noticed in the morning when I start up the car the engine will rev like it normally does when you turn it on but once the needle drops down it occasionally drops down to 200-400 rpm. This also occurs when I break coming up to a stop sign or red light, when I apply the break and come close to a stop the rpm will drop to 200-400. I am curious if anyone has had similar problems and what might cause this? All feedback is much appreciated.