what's intriquing me is the airflow has remained constant (no clutch fan to slip) but something has deteriorated to where the same amt of air ain't no longer cutting it. Some tuning parameter could have been changed (you made no mention of that when asked). pump has been changed so if it was bad so no loss of water flow (unless the rad is partly clogged but as said it would for sure show up at higher RPM's if it was causing a problem). You have confirmed the temp with a mech gauge? Maybe it needs more radiator.