HELP needed - Vacuum leak ?
 

Hi,

when I replaced the air filter this weekend and started the engine with the engine cover off I noticed a LOUD hissing sound every time when I step on the throttle and also when I let off the throttle.

I did the usual tricks looking for a vacuum leak but couldn't find anything.

It seems to me that the noise is coming from the area which is circled red in the attached picture.

Any ideas / hints etc?
BTW: does anyone know the purpose of this big tube which is circled?

Thanks

That tube you circled is part of the intake, specifically inside it is a DME controlled resonance flap. The resonance flap allows the length of the intake air track to be optimized over a broader range of speed. If the hissing sound is coming from there, check the solenoid valve as it activates a vacuum servo that opens and close the resonance flap. (its located about the middle of that tube)

check your brake booster vacuum line, you may have knocked it loose when you pulled out the filter element. its located towards the rear of the car just below the intake manifold on the side of the air filter box.

CEL and single code P1130
 

Just got my first CEL with one code, P1130, while sitting at idle in traffic. Read all the threads so just a quick question. And of course I have to do the CA smog check in the next few weeks so need to sort this ;-)

Engine only has ~25k, but MAF is probably original to car at 60k. No indication of any issues however, rock solid idle, correct behavior when removing oil cap, no smoke, etc...

Is there any downside to clearing the code? Perhaps just drive it for a few more days to see if it clears?

I also noticed what Chris mentioned below regarding a hissing sound from the resonance flap actuation when I blip the throttle from idle. Is that normal behavior, or indication of a vacuum leak that may have caused my code? I do not hear any hissing when it just sits at idle.