Is there a check engine light coming on?......like from a misfire?
Clogged EGR ports could be a cause of misfire.
To verify, remove and plug the vaccum line that goes to the top of the EGR valve.
Start motor and drive the vehicle.
If the problem does NOT happen, then the problem is likely the EGR system.
If the problem still happens, then the problem is not likely the EGR system.
Reconnect the vaccum line to the top of the EGR valve.
This test will cause the Check Engine Light (CEL) to come on because you have disabled the EGR valve from being able to open during this test.