The only thing I can suggest is to try different radios.
I had a weak signal (not just with MIUI) on my DHD, and at home I only had a 2g connection. The latest radio has given me full signal strength and HSDPA.
Sent from the App that Time Forgot
Just re-flash the ROM without a wipe, or get the apk from the zip.
I'm on my phone and can't post the app at the moment.
Sent from The App that Time Forgot.