On the drivers side of your Injection pump is a black piece of plastic that has 2 vacuum lines hooked to the top of it. This is your C6 VRV, and is held on by two bolts. Assuming you've got vacuum to it, loosen the two bolts and rotate it back a bit towards the cab. Then take it for a drive and adjust as necessary til the shifts are what you desire. If this doesn't help, let us know and we'll go from there.