Welcome to the Zone Keith! 
Three things come to mind:
Bad TPS. Since you say the symptom is getting worse, my guess is that a bad spot is developing in the arc of the trottle position sensor. It is feeding bad data to the ECM. As a consequence the ECM makes an abrupt adjustment in the fuel delivery which you feel as a surge.
Coolant sensor mod on a '97. Has the coolant sensor been relocated from the radiator to the thermostat housing on this '97? If not, the ECM will stay on the "cold" map much longer than it should. If you live in a colder climate it may never get on the the "warm" map. This will accentuate the poor fueling in the lower rev range.
Swap ECMs to test for timing issue. This is not likely the problem, but it wouldn't hurt to try it while you have the two '97s together. Do they have the same ECM numbers?
Let us know what you find.
Three things come to mind:
Bad TPS. Since you say the symptom is getting worse, my guess is that a bad spot is developing in the arc of the trottle position sensor. It is feeding bad data to the ECM. As a consequence the ECM makes an abrupt adjustment in the fuel delivery which you feel as a surge.
Coolant sensor mod on a '97. Has the coolant sensor been relocated from the radiator to the thermostat housing on this '97? If not, the ECM will stay on the "cold" map much longer than it should. If you live in a colder climate it may never get on the the "warm" map. This will accentuate the poor fueling in the lower rev range.
Swap ECMs to test for timing issue. This is not likely the problem, but it wouldn't hurt to try it while you have the two '97s together. Do they have the same ECM numbers?
Let us know what you find.
