Had the same thing. My truck would squeal/chirp when it was in v4. Sound was completely random but would normally occur at lower rpm and would stop once back in v8. I recorded the sound and sent the clip to the dealership and they said it sounded like water in the exhaust???? I don't think so. At that point I already had the adapter valve pinned open which did not make a difference. I decided to replace the exhaust with aftermarket and not go to the dealership every week just to hear they could not replicate the issue. The new exhaust solved the problem.