Also, it is very predictable. The 4k RPMs I cited was in drive.

- clear the computer codes (disconnect / reconnect battery)
- drives fine on short trips & medium trips if RPMs < 4,000.
- accelerate into high RPM range (4-5k RPMs), CEL comes on, loss of power at high RPMs, engine rough at low RPMs. The engine problems happen immediately when the CEL comes on, as if a switch was flipped.
- repeat

Is this the limp home mode kicking in?

E.g., the computer detects a misfire at high RPMs and deactivates a couple cylinders. On a 4 cylinder car, losing 2 cylinders causes the loss of power and rough idle. When the codes are reset the limp home mode is cleared & it runs fine until the code gets set again.

It's frustrating in that the only codes getting set so far have been misfire codes.