First post here. My 2004 TB has 106K miles and is sometimes running rough at idle or near idle. Seems to happen intermittently and only when at full operating temperature. It is throwing DTC codes P0014 and P0016. I replaced both the Cam Position Sensor and Cam Position Actuator Solenoid then my mechanic performed the "relearn" procedure and did an engine oil flush. The old CPAS looked somewhat dirty but no screens were missing. After all this, there is no improvement and the DTC codes are still being thrown. My mechanic says the exhaust cam phaser under the valve cover needs replaced. Does this sound legitimate? At $700 I want to be sure. What would be physically wrong with the exhaust cam phaser? Should the timing chain be replaced too?