Exhaust leak?

More than likely this is an exhaust leak. The fact that this is only noticeable when accelerating and on the passenger side tells us that it is the passenger side exhaust manifold.

If could be a joint in the exhaust but more than likely it is the manifold gasket.

Here is a guide that will help with repairing this:

https://www.2carpros.com/articles/exhaust-system-removal

The way to find this is start the truck and have someone rev the engine so that you can hear the noise, then start putting your hand around the exhaust components (don't touch them as they will be getting hot) and feel for puffs of air.

This will tell you where it is coming from.

I attached the process on how to replace the manifold gaskets as I suspect that is the issue.

Thanks