Codes don't tell you what is wrong
Okay... sorry for being gone so long. The problem was fixed once I convinced the dealer that pulling the heads was the wrong corrective action. They finally found a broken wire to the #4 injector, causing what the code says as a too lean of a mixture (ergo, why they thought it was a valve). Fixed wire, problem solved. Driven to Charleston and Boston with no repeat, no problems. Great little car, now!