The code read P0401 and it said "EGR flow insufficient." I changed the EGR and reset the code, but the check engine light keeps going on after a couple of hours. Please help!!!

You need to take it to the dealer and have it cleaned out....just replacing the EGR valve won't fix it....and if you leave it on there long enough without getting it cleaned, that one will mess up to.

The code read P0401 and it said "EGR flow insufficient." I changed the EGR and reset the code, but the check engine light keeps going on after a couple of hours. Please help!!!
Clean out what?

The dealer has to remove the intake plenum and clean the egr port. They also install a metal sleeve into the plenums egr port so it doesn't coke up as easily. The ports tend to plug up solid and set that code.