we found the wiring harness was rubbed thru against the frame near the motor mount. One injector was out of whack (intermittently) as a result. repaired harness, problem gone.
Note: there was recall for this problem of the wiring harness running thru on the 2008's. Mine is a 2009, and even tho it is EXACTLY the same issue, I get no warranty. Go figure. ME and the Yamaha rep are going to have a talk ......