I don't use BoP and i tried disabling Special mobs and infernal mobs etc....still the same....i tried disabling a bunch of mods and no luck....its too time consuming like you said.
Please try this: If you have a world.....then observe your RAM while not moving in game.Also please let me know how much RAM it uses as single player in your test.
Graphic settings are set to low....fast graphics...not fancy....
Also its not the update causing this.....this problem was still there in 1.1.8...after the update it got worse.
I did test that. Its part of what I test when making a pack.
If I give it only 4GB of RAM the max it reaches after 2 hours is:
If I give it 8GB of RAM the max it reaches after 4 hours is:
All of the 1.6 packs except Lite2 are suggested to have at least 3GB of RAM. Vanilla for 1.6.4 recommends 2GB with no mods added.
The above were done at Fast Graphics, Max FPS 1920x1080 resolution ,with a 64x resourcepack and all mods enabled in SSP on the world I play for testing the pack. Not sure which setting you are adjusting for "low". I do not use any jvm arguments at all. My computer can power through just about anything though. Typically if you can lag my computer with a mod, you need to re-write the mod.