I have been following XDA for years now and have always been able to find answers to my questions here regarding flashing for a HTC Desire, Galaxy SII or my current Galaxy S4 I9505, rooted running a 4.3 GPE rom. Baseband is XXUDMB. Recovery is CWM 220.127.116.11.
After following the thread GOOGLE EDITION 4.4.2 by Danvdh, Kryten2k35 & Ktoonsez
I decided to flash. Love this rom, it's superfast!!! One thing didn't work for me: the phone kept losing connection with my Dutch mobile carrier Vodafone (no data, phone calls not possible), especially after locking the screen. To my understanding the rom does not ship with LTE of GSM modems, so it should not be the problem that a 4.4 LTE modem causes sound, data or WiFi problems when on the "old" bootloader (pre KNOX). After flashing the baseband still shows XXUDMB.
I tried *#*#4636#*#* and setting network type to GSM. However, the menu is not the same as my current 4.3 and the option LTE/GSM auto (PRL) is not available.
Reverted back to my 4.3 rom for now, but really hope somebody knows how to solve the issue.