It's DawnGuard that's the problem with lag. My old 11 MB save jumped from that to 15 MB with all three DLC. I did all the quests and LAG, LAG, CRASH. So I made a totally new fresh guy(reinstalled everything), everything was fine until 8 MB, lag, lag, no crash, but lag. Reinstalled everything and deleted that chracter, but I didn't install Dawnguard....my file is 11 MB and really smooth, only a few quest bugs, gonna make a fresh install for a new guy after 1.9... Let's how that goes with no Dawnguard.
Bye Serana, Crossbows, armoured trolls..... WHYYYYYYY