yasha :
Ideas about what? I think you should test your RAM with GTA running. I don't think you will run out of RAM. Look for usage number below the chart, or "Available" in the separate box below. I guess 1.8GB at idle is high, but still that shouldn't cause any problem for GTA IMO. You can do some maintenance stuff to reduce your system RAM usage (possibly you have higher CPU usage too because of processes running). For the problem at hand, test RAM while GTA is running. If that's the issue, you have to buy more RAM. If not, more digging to find out the actual problem.
TO SEE "FREE" RAM IN WIN 8, GO HERE
THEN HERE
AND FINALLY HERE
The way I think about it is like this: I have 32 GB of RAM, and 22 GB is free, so 10 GB is somehow occupied.
The game will probably 2-3 GB when running, so things will shuffle in the background if you have 500 MB free, which can cause stuttering. The same goes for VRAM.
What's your "free" just after a fresh boot-up, and what is it while the game is stuttering?