It is for sound control. The vast majority of these cars are sold to folks that do not want there engine making odd and annoying noises everytime you back off the throttle. I have been hot rodding cars for 40 years and I don't like noises from the engine that do not contribute to HP gains so mine is staying hooked up.Is it an emissions thing? I am new to Turbos why is the blow off valve even have tube running to it from the intake?
Everytime I hear one I think Ricer.