I'm quite befuddled as to why my computer can't handle a game that was made in 2008. I've been using the Game4Video ENB, perfect for ELS but it makes my game lag horribly. My computer specs are:

ASUS R9 270x 2GB

8-core 4 GHz processor

8 GB of DDR3 RAM

I'm running it on a 2 TB HD

I've tried disabling the Windows even log stuff and I'm even using a commandline but that's still not enough. I get average 20 FPS at night at 15 and below during the day. I've seen people that have worse/similar pc parts that I have but can run the game better than me. I'm just at a loss and don't get why GTA 4 wants to run so horribly. I can run BF4 on ultra and get a steady 60 FPS, same for Skyrim. If anyone has any help for me, please explain this.

A lot of these issues are not related to hardware, it just comes down to how well the code for the game was written. This is a common issue when I play Flight Simulator; the stock game by itself runs smoothly however when you start introducing addons and making the game do things it was not designed to do then you run into issues. Also GTA IV is a 32 bit game so it can only take advantage of up to 4GB of RAM regardless of how much your computer has installed.