Just want to confirm I'm thinking of this the right way. I think I have a vac leak.

When I start from cold, the car runs fine, but once the engine has warmed up, after a drive, there's a loud hissing coming from the engine. It's coming from around the right hand side of the plate at the front of the inlet manifold. I've done a pressure test on the pipework and valves on the plate only, and they hold 15psi fine with no leaks at all. I even tried activating the valves with a 12v supply and it still held pressure OK.

Is there anywhwere else that's a common place for a leak. I'm presuming it's in the mass of pipework that makes up the suction jet bullsh*t, but I can't get to it to check it over. I'm guessing I'll need to take the mainfold off.

I've scanned it, and the fault is Add fuel trim too lean, which would make sense if it is a vac leak.

p..s The 'y' breather on the cam cover has already been changed as it was split.

The S shaped breather pipe is the other likely candidate, it joins onto the Y shaped one and the other end connects to the inlet manifold.

Basically if it is giving you that code, one of the vac hoses to the manifold is letting in unmetered air when the throttles closed

Cheers dude!

Had a look a few days ago, and found it was the other lower pipe that had a big split in it, maybe 2" long. Its the one that goes from the 'T' piece to the inlet manifold. Got a new one from sere motors. I can definitely tell the difference in material. The old one has gone like blu-tac. Bought a new dipstick holder too, as the old one is cracked too.

Was going to get a silicon one from ebay, but couldn't find any cheaper than the OEM one, and that lasted for 9 years.

All fixed. New pipe is on, turned the EML light off with vcds, and it's been off all week, and no hissing. Decided to change the whole lower system, including the valve, and I'm glad I did. The old bits were looking a bit sorry for themselves, and full of soot and oily mayo etc. Not nice!