When I change gears, let's say at 2000 rpm, while the car goes through the neutral zone, the rpm's actually increase by approximately 1-2 hundred rpms.
It's the infamous RPM hang found in Mustangs. Nothing to worry about but if it's annoying to you, you'll have to do the IAC mod. This has been discussed before so if you do a search on copper pipe cap, you'll see what I mean.
The IAC mod rules. The transmission would sometimes grind when I used to upshift because the rpm's would increase when pressing in the clutch. The IAC mod fixed that problem.