Ok, so something is definately not accurate with the dates given in the OP.
I just got another GT40 upper and lower today that was off a 97 and the stamp on the car and on the intake said 1/97, and the intake is the EXP 1 intake with provisions for egr, BUT, I also got the heads and they are GT40 P heads, not GT40.
The OP said that the GT40P's were not used until they started using the EXP 2 intake in March of 97, and I got a pair off one that was 1/97. It was also stated that the EXP 1 intake was not used after Feb of 97 and I got several EXP 1 intakes with privision for EGR that were off late 97 explorers and 98 explorer.
So if you are looking in the junkyard for one, don't got by the tag on the intake or on the door,.