Here's something to try. (I didn't use PST since I'm only really familar with ODIN and it seemed to work for me).
1) ensure you are using ODIN 1.82. I was using ODIN 1.3 earlier and it seemed to have some issues. :-/
2) using the original ED1 tar file from here: http://forum.xda-developers.com/show....php?t=1087342
download and extract the .md5 file
3) Connect your phone, place in download mode and run ODIN 1.82, under "PDA"
select the .md5 file you downloaded and extracted.
4) Remove SIM card as the directions in the above link state (I dunno if required)... but put your battery back in. I think this is REQUIRED when flashing lte_modem.bin part or the files.
5) flash with ODIN and restart once completed.
This reset my phone back to ED1 completely, including writing ED1 modems, which... prior, had been stuck on the EP1F leaked versions. :(
I suspect it will do the same for your lack of baseband, too.