So an 1200 mile drive seemed to partially address the problem. At least the surging/revving problem stopped. But was replaced by a low idle. It idles just under 500rpms now. I also took a closer look at the connections to my ECU, and found two connectors that were a little loose when I tested with a pin of a similar size to the ECU pins. I popped the wires out of the connector block, as advised in an earlier post, tightened them up, and put them back in.

I also discovered that one of the "splints" that slipped between the wire pairs in the connector block was inserted in the wrong place (between two empty connections in the block). I moved it back between the correct wire pair, and things seem a little better.

I'm still a little worried about the low idle. I'll be checking the voltage and connections to the idle speed control module next.