u/Anonymous_man7

I’ll try to keep this short, was double checking the size of my muffler on my gmc sierra since I was gonna swap it for a valvetronic and I found this little spring on the side that I can turn roughly 90 degrees and feels like it’s turning something in the pipe, when I let go it turns back since it coils the spring, not sure what this is but right before the muffler the pipe is stamped “Adaptive Valve” anyone know what this does?