I have done a number of boost leak tests and have been successful in tracking most of them down. Today I replaced one of the BOVs as the diaphragm was busted on one of them. I was hoping this was the last leak but not so. I have my air compressor set to around 10psi and I can hear a heap of air hissing from around the central portion of the Intake manifold. I have tried to squeeze my fingers in there as best as I can but can't feel any air. I sprayed some crc in the area but nothing is blowing back in my face. Anyone had a similar experience? I have 14psi actuators on the waste-gates but it is only boosting to below the 7 on the stock guage. Not sure what that is but guessing >10psi.
haven't had the same problem but if it's leaking from the centre of the manifold, do you mean the upper plenum? then it's probably got a loose bolt or two around it. Check the torque on them or the gasket has been damaged on it. What about some soapy water sprayed onto the area in question?
The soapy water is a good suggestion, mix some detergent & water in a spray bottle, it works very well.
Have you tried the old "rubber tube shoved in your ear hole while you move the other end around to localise the noise" trick? Stock boost guage is around 9 psi when it's just under the 7, assuming it's working properly. Does the needle rest in the centre with ignition on but motor not running? I finally got my mechanical boost / vac test guage returned by the last borrower so you're welcome to grab it dude.
funny, I have just completed a plenum pull yesterday after suffering a very similar leak to what you described. Ended up being two stripped threads on the lower plenum (for the upper plenum bolts) that I had to tap a UNC thread into & install new bolts, however in hindsight I think Helicoils would be the better option.
Ok, closer inspection revealed the problem. Somehow I managed to forget the 4 front most bolts on the lower plenum when I assembled the engine!!
