p0170 fuel trim malfunction bank #1?

check for vacum leaks,o2 sensor operation,air flow meter reading,this is a lean code

you really need to look at actual values to be certain what is going on. Look at fuel trim part load and fuel trim idle. If they are going in opposite directions, in other words, richening in part load and leaning in idle, this is a dead give away of a bad MAF sensor. Replace with new Bosch unit specific for the car. People will try to sell you on an insert,at a cheap price, but this insert is actually taken out of a VW Sensor (the wire harness will connect, but you will notice that the lock tabs are wrong, this was done on purpose, I have heard it all usually the claim is it is for a European car). Bosch does not officially supply an insert. Each insert is calibrated to the size of the housing, VW being much smaller, the fuel trim will be off, it will work but in my opinion not the correct way to fix. I am a Bosch Authorized Service Center, so I know what I say is true. Spring for the extra money and fix it right.