feels like its running out of gas, jerking from power on to power off and back over a period of maybe a minute. ...and then it went back to running fine. This happened 2x during a 1500 mile road trip in 90+ degree weather. Both times this occurred at highway speed. A preliminary scan indicated that the engine was running lean on both sides of the V6, but the mechanic was (of course) unable to replicate the problem. Anyone else have this issue? Is it something a dealer would have better chance diagnosing??