DTC Codes

I had my SES light come on this morning while going to work. I stopped by my nearest Advance and had them check it out. I had the following codes.

History DTC P0102 MAF Circuit Low Input. MIL not requested.

I cleaned the MAF as the little bobbins looked dirty on the air cleaner side. All voltages were correct at the plug for the MAF as well. So I hope that fixed that code.

History DTC P0141 & P0161 Bank 1 Sensor 2 and Bank 2 Sensor 2 O2 Sensor heater circuit malfunction. MIL Requested

This seems to be an intermittent problem and I checked the voltages and appear to be good. I am going to change these suckers out as they have

95K on them. They usually will come on when it is cold outside. It was in the high 40's this am.

Transient DTC P0340 Camshaft Position Sensor A Bank 1 Circuit Malfunction MIL not Requested

I have no idea what is bringing this on or how to check it. I haven't had the distributer out for over a year and never had this code before. In fact the only codes I have had were the 141 & 161 codes. Can someone point me in the right direction to troubleshooting the P0340?

Thanks :)