You said you it reverts back to 1x when you are in the "downriver" area? What part more specifically? I have posted in a couple other threads about getting the 3g icon (slightly faster browsing speeds) and I live in the same area you say reverts back to 1x. I primarily am in the Taylor area (Allen & Goddard), but have had the icon in all surrounding cities.
Like the above member said, I would put prl 3025 on it and see if there is a difference. Also stated in other threads about people I know (in my same area) having 3025 automatically updated to their phone. Glad to see more members getting the slightly faster speeds, but the speeds vary quite a bit.