I think I know what this means but I would like to have some more input. Is this what makes the intake so loud when the exhaust brake is engaged? Is there really any reverse flow in the intake when the brake is engaged? Inquiring minds want to know

 

Yes, some exhaust gets pushed into the intake when the exhaust brake is activated. There's no boost, but there's up to 60 psi trying to push exhaust out the intake during overlap. It doesn't get to the point that exhaust blows out through the air filter, remember that while one cylinder is in overlap, another is on the intake stroke. You just get some soot in the intake, not reverse flow.