I pulled the error codes and saw one for engine knock (could have many causes) and two for traction control. I expected the TCS errors because I pulled the TCS fuse and fusible link years ago due to a run-on TCS pump. But one of the codes was new, for the secondary throttle position sensor.
I got out the service manual to see what the secondary throttle was and where it was. It is the business end of the TCS, the device that cuts the air to the engine when slippage is detected. A check of the system wiring diagram revealed that it that the secondary throttle, which is controlled by a small motor and a return spring, could conceivably close even with the TCS fuse pulled. According to the manual, the return spring should keep that valve open unless the motor is pulling it closed.
I unplugged the secondary throttle motor and sensor. Both connectors are right on top of the air intake, so you don't even have to get dirty and it takes a few seconds. I've now driven about 200 flawless miles. So this was probably the correct fix.
Rather than leave the connector sockets open, today I cut two fingers off a disposable rubber glove and made connector condoms.
With the condoms installed over the sockets, and the excess stuffed into each socket, I partially mated the male ends so they won't collect dirt either.