I was getting a CEL with codes for P0140 and p1411. Also the Blower for the Secondary Air Injection System was loud, like a vacuum cleaner with a blocked suction. First I replaced the blower, but that didn't change anything. Next after some research and double checking the vacuum lines I tried replacing the Electric Change-over Valve. I'm running fine with no CEL now and the blower is sounding normal.
Best access is by removing the alternator I kept it wired, but pulled it forward out of the way.
1. Remove the panel behind the seats.
2. Remove the serpentine belt.
3. the Alternator is held in with 2 bolts. The one on the right runs through an idler pulley.
4. With the alternator removed you can access most of the SAI system. The change-over valve is circled:
The valve clips onto a bracket at the bottom. There are two vacuum lines and one electrical connection.
The hardest part was getting my big hands into position to connect the vacuum lines.
There are a few more parts of the system, that can fail, or the passages in the SAI can be clogged, but this seems to have fixed it for me. I'd say #1 check the vacuum line for a leak before replacing other parts. While you are in there it's a good idea to replace all of the vacuum lines anyway if they are over 10 years old.
Here's the basic diagram, but layout varies by year and transmission:
