Engine coughs

Add about a quart of Robitussin to each tank, and apply a full jar of Vicks to the air filter.

 

"Coughing" is usually associated with exhaust restriction and air flow actually stalling through the engine and reversing out the air cleaner to produce that sound. Only the turbo actuator has the ability to change and restrict exhaust flow like this on a temporary or certain conditional situations. If the exhaust after the engine was restricted, this is more permanent and would cause performance issues all the time. Make sure all your sensors are clean and your turbo actuator is working normally.

 

Yes, it is air actuated and only uses air when the engine is actually running, so it can be hard to find a leak. You can actuate it with the key on with Insite to check for any leaks and proper operation.

 

I have an older ISX with an air actuator.
There is a filter on the drivers side to filter the air to the actuator. I had mine changed and it was plugged up, my boost went up significantly after.
Not saying this is the problem but you never know, I know the shop didn't even know.
It is a very short filter.

 

It is just under the compressor. It is a small, short filter fairly easy to see. You may think it is being changed when the truck is being serviced. Follow the air line from the actuator backwards.