So I had this problem of a weird hissing noise under boost. I just converted to simplified sequential and replaced all the vacuum lines hoping that this would solve the problem.

I took the car out last night for the first time, and the noise is still there. The weird part about this noise, is that it sounds like its rushing air out of the vent near the vents on the door. There is definitely no air coming out though. At first I thought it was a huge boost leak, but the area of the sound just makes no sense to me.

Is it possible that it's just turbo noise and the acoustics travel around the engine bay to that area? My passenger said he heard the same thing on his side in the same area.

The car is also maxing out ~6-7 psi. I did some searching and it looks like the "pills" inside some of the lines were the cause if they were missing. I found 2 while I was doing the conversion, and replaced them in the same orientation. Are there more than 2 or could this 7 psi max be something else?

Thanks in advance.

 

There are only 2 pills. Sounds like a boost leak to me

 

^I agree. Check you plumbing and couplers, especially at the 'Y' pipe to crossover.

 

you Probably Have a boost leak , Like stated above you should recheck everything

 

Already replaced the Y pipe coupler. I guess I'll have to pressurize the system and try to find the leak.

 

check all the vacume joses , check the upper intake manifold for loose hoses or caps

Checck the interccooler couplers for cracks or loose clamps

 

Hmmm. I did notice the hose at this location seemed to have a lot of movement when I was putting the intake box back on. Perhaps the rubber has worn/stretched and it isn't sealing properly.

 

replace it if you think it may be the issue you can get I think its like 3/4 inch hose it will be a very snug fit but it will go on .

 

its probably split on the bottom, it could totally be your problem

 

I'm hoping that it is. It was just really odd how the noise sounded like it was coming in from the cabin by the brake booster.

 

noise is funny, vibrations transmit. my FCD (FC with REW) has a bad booster, and it does make a hissing noise

 

Well I replaced that hose, and boost still peaked at 5.

Then I did some inspecting and found a tear in the coupler from the y pipe to the intercooler.

Replaced it with a silicone one, no hissing and full boost!

 

Congrats