As everyone is aware the 4.2 xkr like others has a valve system exhaust. More power and vacum causes a valve on each side of the exhaust to open with more noise. Pulling fuse 19 leaves it open all the time. Each valve mechanism has a rubber tube for each side connected to valve part to supply vacum. The vacum tank is located above the left rear wheel arch, behind wheel arch cover.
Question is, if a car is fitted with a aftermarket performance back muffler WITHOUT the valve system do the tubes that are no longer needed have to be blocked or left open, does it matter. If fuse 19 is still in, would air be coming from tubes trying to create pressure. Would it be better to remove fuse leave holes open. Does this effect anything.