Hello there!

I've quite a strange problem:
Currently I am running a bunch of mods (I guess 160 merged down to 100) without many problems except one:
after a while NV becomes a lagfest and I have to use the pcb-command to keep playing.
I noticed that for some strange reason NV only uses 1.7 Gb of ram.
This seems strange to me, because it never went beyond that number while lagging like hell.
Anyone has experience with this problem?
I tried the 4gb patch, the dedicated 4gb exe but 1.7 Gb seems like my personal wall.

Same here, but pcb won't solve frame rate drops and stuttering for me. I'm stil try to figure it out. I post again if I find the possible answer. GOG version already have 4Gb patched so It must be one or more from the mods, or maybe missing mods that fix the memory problem. etc.

Don't use the PCB command. Get to Nexus, install the Mod limit fix it will help your performance regardless of how many mods you have installed. I hope you have NVAC, Tick fix and the like installed. But, no matter what, you should not play a prolonged period of time without restarting the game. The New Vegas engine can't handle it.

Not only is the GOG version already 4GB patched, the communtiy 4GB patch is meant for Steam's version which doesn't come fixed. Adding this patch to the GOG version can thus actually break the GOG version, so make sure to remove it, delete all folders and mod manager folders, and the game's other folder in your documents folder, then reinstall. Then make sure the game runs ok without any mods at all, let alone 160!!

Also, for anyone who doesn't already know it, a good online resource is the Youtube video by gamerpoets titled: Fallout New Vegas | fps and stability fix

The stuttering/lag is probably unrelated to RAM usage or the 4GB patch.

With that many mods nobody here could really know what's going on. I think streetyson is right, you may need to go back and make sure the game runs okay without mods. If you do a fresh install and the problem is still present, then it's not a mod problem. Your paging file settings could be the problem, even. Otherwise, with 100 mod files (plus 60 merged into these?) the only way to figure out which one causes your problems is to do a mod install piecemeal after a fresh re-install of NV. Back up your files before installing each mod and test the game for the problem after installing each one.

Also, most modders will include information about known issues and bugs on the mods you have installed. That might be a quicker place to start, to narrow down which mods to test first.