I tried many customized roms from the 4pda forum.
Some roms (like ViperOS) does not provide 4G LTE network at full speed, so i changed some LTE values with the QXDM program (NV 06828 - LTE BC Configuration).
I'm searching for the original lte_config value to restore it. (My phone is M721H that comes with Flyme 126.96.36.199Global rom for France).
Do you know what is the default value (on Flyme 188.8.131.52G) ?
oops I just found it because i restored my XQCN backup file.
Original QXDM values were :
LTE BC Config : 687195291861
LTE BC Config DIV : 687195291845
original *#*#4636#*#* setting was : LTE/TD-SCDMA/UMTS