I’m 2 years late to the party, but I read through a lot of these comments, not being able to find a solution. After some digging I figured out the problem. I just purchased Turtle Beach Stealth 600 Gen 2’s and they were working great until I tried to use them in game chat (MW2). Party chat worked fine, as most folks previously stated, but game chat was a no go. I eventually stumbled upon a video that fixed the issue. If you’re on Xbox, go to settings, then select general, then select volume and audio output, under advanced settings select additional options, and lastly enable the “allow passthrough” option. Hope this helps anyone with this problem.