You are hearing whistling noise when Jake brake on 2007 dually?

A whistling noise when using the Jake brake on a 2007 dually could indicate a few potential issues. It may be caused by air leaks in the exhaust system, worn components, or a malfunctioning brake valve. It's advisable to inspect the exhaust system for any leaks and check the Jake brake mechanism for proper operation. If the problem persists, consulting a professional mechanic would be a good next step.