What is under vacuum in open loop that isn't in closed loop?

I can hear a whistle when I start the car, and as soon as it goes into closed loop, it goes away. I have checked all over and can't find the leak.

Any ideas?

 

its your air pump commmg on and then going off once the car goes into closed loop

 

can I program that out ya think? I deleted EGR when I had the motor out. just not sure what I am looking for on the AIR pump. Is it a vacuum leak then or is it just the noise I should expect?

 

I get the same EXACT noise, but once the car warms up it goes away, but when it was in open loop before, i didnt think the whistling was this bad, mines pretty loud, i hate it! Also my mileage has dropped off bigtime, i wonder if thats at fault! i cant wait to get money to get an ls6 intake and get rid of egr and air!