Ok, it looks like the problem was with the oil saturated air filter. It is a foam style air filter so soaking it in paint thinner cleaned out the oil and dirt, and after letting it air dry for about 30 minutes, the power up-power down problem was fixed. A squirt of carb cleaner was shot into the carburetor with the filter off and whether that was any help is an unknown but it didn't hurt.
I over-filled the oil change with a little too much oil and probably the engine sprayed it up through the carburetor and into the air filter. The engine sensed the lack of air coming through the filter and opened up the choke plate which is why it was going through a power-up, power down back & forth what with a clogged filter and the choke making automatic adjustments.
There will be a pop quiz on all this tomorrow at 10-am!
And, it's a Weed Eater 22", $129 Wal-Mart lawnmower on it's third season now. Wal-Mart warranties them for 90 days, and I managed to destroy the engine on the previous mower on about the 85th day by hitting a rock with the blade, and Wal-Mart didn't bat an eye about replacing it with a new mower because I had the receipt! Rots-o-ruck trying to do that at Aubuchon's. Gosh, what was life like before Wal-Mart?