Obviously, a tune-up if you haven't done so in a while.
After that, I would check the ignition system. Check the plug wires and resistance check the ignition coil.
A vacuum leak would cause issues all across the board. Issues that surface in the upper RPM range tend to fall on ignition issues. EGR is dis-engaged on wide open throttle, so if you suspect an EGR, you would see if the lag is there on partial throttle versus wide open, but again, an EGR issue would show problems all across the RPM range once the engine warmed up.