You must've not flashed the conversion to sprint properly:
[ROM][WIP][ALPHA] aospCMod | AOSP 2.3.4 / CM7+ (Gingerbread) - Page 42 - xda-developers
Before flashing:
Format all 4 partitions under Mounts and Storage (Boot, Cache, Data and System).
Order to flash:
AOSP Rom
aospCMod-OV-to-sprint-signed.zip
Gapps
OV-to-sprint-20110403-signed.zip
Note: It is recommended that you use the Xionia Recovery, I had problems with other recoveries when trying to install and was told to use Xionia which fixed my issues.
Also, this rom doesn't come with the default mms app so you need to download something like GoSMS off the market.
I don't use bluetooth headsets so I can't give any info regarding that, but plain headphones are A-OK.