What I find puzzling is that I was able to drive it 45 miles with no codes. Then the P0304 happened almost immediately after changing the mounts. I swapped in another coil, cleared the codes, and the P0304 happened again within a couple of minutes. Then I swapped the plugs and moved the #3 coil to #4 and put the original #4 coil in #3, cleared the codes, and the P0304 happened a third time within a couple of minutes.

There is another weird symptom, that has existed since last year. After clearing codes, the car won't start (like a bad immobilizer...runs for a second, dies and no start). After doing the clear code process a second time, the car starts. This happen once last summer, after a NJ gas station attendant didn't put the cap on properly. Then, no problems with the car for 5,000 miles until now, and after clearing codes, I see the same weird need to clear it twice.