Try letting go of the gas in first gear at 2k rpm and feel what happens just as it drops under 1.5k. What I get is a rumble of the exhaust and the car slightly jumps ahead as if restriction is removed. Perhaps emission / dB control? no clue
Noticed in 3rd, 4th, 5th gears, rpm in around the 1500 range feel a tad flat, as if car is holding back…..otherwise acceleration and rpm climb seem fine. Car has 1700 miles, driven almost daily, in all weather, but garaged at night.