Manual Transmission - RPM Increase
 

I have a 2006 Hummer H3 with a manual transmission. Recently, I've noticed my RPMs continue at the same pace, or increase, when shifting and then staying in neutral. For example, when coming to a stop and shifting to neutral the RPMs remain at approx. 2300 and more recently have started to increase to 2500. The RPMs continue at this pace for 5-10 seconds and then go back to the normal idle. This is a fairly new/clean vehicle with only 27k miles on it. Any ideas?