Ditto on all ksg said. I would add checking the air intake passage if the clamps are tight or perhaps a crack tube. I had the same error code and replaced the plug wires, plugs, oxygen sensor, egr valve. My idle was rough for most part. I even paid the dealer to diagnose the P0170. They wanted to replace the oil pump. It did not make sense so I took the car to another mechanic. My problem finally turned out to be a leak in the throtle body gasket. I spent over $500.00, and it turned out to be a $2.00 gasket. Ain't life great?