Hi Jim, I have compiled and ran your code on a Seeeduino Mega, with the "Arduino Mega + Duinos" board selected, and I obtained the following results in the ID terminal:
Pump Pressure = 12.50
377 589 533 496 696 759 819 701 1 764 1 519 1 998 3 544
Pump Pressure = 12.50
360 606 572 494 652 760 863 721 1 552 0 118 2 964 3 514
Pump Pressure = 12.50
349 619 565 474 646 780 933 723 1 542 1023 501 1 902 1 684
Pump Pressure = 12.50
349 617 567 480 643 773 922 721 1 542 5 335 1 949 6 512
Which board and settings are you using?
Regards,
Julián