Hi all, I drive a 06 Evo IX MR and it was driving good. Drove it fine all day, Went to a local meet and ran a few cars. Everything is still fine.

When I was just about home my car started to rev up and down as I wasnt in gear, then started happening in the gears. And now its has a high Idle and will drop, Almost stall and rise again up to 2k.

I can hear this loud hissing or leaking noise coming from the rear passenger side of the engine.

I checked vacuum/boost lines and it all seems to be snug and good.

AFRs are at 22 so its really lean. (This is at idle and shut car off immediately)

I cleaned out my IACV and there was no difference in the way my car is acting. Im stumped and a little worried.

Any suggestions or previous experiences? Please help.

Heres a video through photobucket, Just click the picture.

 

Do a boost leak test and report back.

 

Boost leak test was done last week. It all checked out good.

 

Sounds like a vacuum leak, maybe not from a disconnected vacuum hose. Try and locate the hissing. More than likely you'll find your problem. Check your gaskets around the area.

 

Even if your boost leak test was completed a week ago, you could have blown a gasket or hose between then and now. Boost leak test it again, more than likely the problem will show itself.

 

check the vacuum lines on the back of intake manifold