Elusive P0402 issue

Replaced the cylinder head on my 1998 DLX 2.7L 4x4 taco (as well as a lot of other parts) and before I did that P0402 (excessive EGR gas flow) was not present as a code, though I did have catalytic converter code, probably due to being poisoned by a massively blown head gasket. After rebuild I get P0402. The engine runs fine with no sign of hesitation and gas mileage seems OK, so seems like a faulty sensor.
I have checked the EGR which makes the appropriate moving sounds as I apply and release vacuum using the mityvac, and the engine nearly dies when I apply vac when it is idling. So probably not the EGR.
I tested the VSV with the mityvac and showed it holds vacuum until I apply 12v to the electrical connector when I hear the valve click and the vacuum releases, so probably not the VSV.
I tested the EGR temp sensor which reads 200K ohm when cold using a digital mutimeter. So no short. Anyone know what resistance it should be when cold?
I checked all the routing of the vac lines, and checked for leaks, but can not find any problem.
What else can cause P0402 to set with no symptoms? What other tests can I try?