Error Code

I have a 2002 Dakota, 4.7 v8. I have a error code, (Auto Zone said it's P0422) stating there is a slight vacuum leak in the fuel system somewhere. I've replaced gas cap & a hose underneath the truck at some box where the hose was cracked. The error code still comes back. Has anyone had this problem? What could it be?

had that kind of code on an explorer, turned out to be an intake gasket leak