I've already tried setting FalloutNV.exe to high priority in the task manager and just about every other suggestion related to these two problems that I can find on here, but nothing helps. When I fix one, the other returns, which is really frustrating.

I've concluded that the d3d9.dll file in your game folder is somehow related to both these problems (at least for me), but I can't come up with any way to fix both of them. Here's the catch: once I used that new d3d9.dll to increase my FPS, the audio problem returned! If i switch out that d3d9.dll for the one that came in the audio fix download, the audio problem is fixed, but my FPS go back to being crap. That file works brilliantly to fix slowdowns and my FPS is good. I fixed this using the d3d9.dll file found here. Anything I can do to fix this Ive updated my video card and all that shite. Even on medium settings, it will lag but the wierd thing is that I can play Fallout 3 on Ultra settings with a smooth 60fps. However, when I started the goodsprings quest where you fight the power gangers (or whatever it is), I encountered massive slowdown and the game became to laggy to play. Having a really bad lag issue with New Vegas to the point where its not tolerable. Afterwards, the FPS stabilized at 60, but the game stutters. But I hate playing without vsync because the video tearing is unbearable, so I enabled it. The game normally runs with 70-90 FPS on highest settings when not using vsync.

Oddly the file is actually some kind of patch for another game, but after using that download, my audio worked perfectly. I'm playing Fallout: New Vegas on a decent machine. I was able to fix them completely using the download and instructions found here. Ok, so I have encountered the same audio stuttering and delays that many people are posting about on here.

Fallout new vegas lag fix