This is a real mystery in terms of the 3.5 and 5.0. I believe the 35 leaves the 2nd exhaust closed most of the time - including startup. Whereas the 50 has both open on startup and then closes one down. SOME have said that they noticed reduced power with the golf tee mod. Some have suggested that the entire reason for closing one exhaust is to warm up the catalytic converter faster - which would make sense I guess. Either way, there is a vacuum actuator on the exhausts that open them up.
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2011 1M, Black loaded sans sat radio
2021 911 C4S Gentian Blue, manual
2023 X3 M40i - loaded sans Park Assist
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