If you're running the TSOP bios, you have to make sure that your MS Dash is labled xboxdash.xbe, as this is the default setting. Rename your Evox dash to evoxdash.xbe.
Oh, and don't forget to set the TSOP as the default in OS2 B2, then turn the power off. Now when you turn it back on, it should boot right to the MS dash, if you have turned Instant Boot on.