Yup, no way the IGP is actually *using* 4 GB of VRAM. GTA V's settings will list the VRAM that different settings require and if yours says 4 GB of VRAM, your setting are *way* too high. And quite frankly, I'd be shocked if the game was running well; an HD 5500 integrated is going to struggle to even reach 30 fps at 1024x768. That's the more likely reason it's running poorly.