I recently installed a boost gauge and A/F meter, along with a Blitz DTT-DC. I've noticed that after the installation, when I enter boost I can hear what almost sounds like the AC kicking on (much louder, like AC setting 4), but no air from vents. I thought at first this might be the normal sounds of the turbos, and since I normally have the radio on, I might not have heard it before. It comes from the passenger side, near were the turbos are it seems. No loose vacuum hoses are apparent, and I'm getting 8-10-8 boost... any ideas or should I just turn my radio back up?

 

Any ideas on this one?

 

I took it down to the local rotary shop and let them have a spin. They seemed to think it was a vacuum leak (which I told them it wasn't.) After they check the most obvious of hoses they said "well it must be the pre cat clogging up, might as well throw a down pipe on there..." This is an upgrade I'll be performing anyways, but these guys are shady and seem to be in it for the money. I had the check engine light pop on about a month and a half ago, for a day, then went away. It ended up being the EGR switch (code 16). Is it possible that this sounds (like a pump kicking off during any kind of boost) be caused from the EGR being stuck open, though the CE light hasn't been on since? And could a clogged DP really be a viable answer to this very annoying problem?