What are these?

[Chetzki]

What are the blue and yellow plastic filter looking bodies under my driver side fuel rail cover? One appears to be a check valve because I can only blow through it in one direction (toward the air intake manifold). What is the recommended replacement interval for these? I'm doing a bunch of PM right now and ran across them tonight. Never noticed it before.

This is an LT4 engine, but probably shared with LT1.

Thanks,
Chetzki

 

[Rabbit]

That's a vacuum check valve for the A/C/heater. I don't know if has to do with the cruise control. Anyway, it's usually the culprit when you have a problem with the heater-a/c doors going to the default position. Apparently heat kills em. I think they run about 6 dollars at the dealer.