Did you mean modified ROMs or kernels? Even I used this in CM the battery drain was a little worse I guess.
I really don't know which app would be consuming a lot of battery. Only apps I would say is google play services and WhatsApp. And also I'm using android l keyboard.
How do you get the BBS app to tell you what is causing drain? I've flicked through the various options and it lists lots of stats, but how do you know which are problematic?