What is the effect of an engine with low 'subpressure'?

[keesiev]

My s3c is running very lean. Each time when I change the mixture of fuel and air to more fuel, it adjusts itself after a while.
After an investigation my garage told me that the engine had a very low 'subpressure' (don't know the exact english word)...
Can this mix up my engine management and cause the lean mixture, and therefore the bogging down at low power?
What is the effect of a low 'subpressure' on an engines functioning anyhow?

[Boosted LS1]

I haven't got a clue what he's talking about. Could he mean sump pressure, ie the vacuum in the sump? Piston ring blowby effects this as do a number of other things.

It would be good to clarify his terminology?

[keesiev]

Sorry for my limited English...Another word for 'subpressure' might be strong 'vacuum'?

Maybe it helps if I try to explain what my garage suggested (with the risk of making my story even more blurry...): the said the seal of my air inlet was not good and should be exchanged.

[Boosted LS1]

Ok, he is saying that there is extra air leaking into the inlet ports and you need a new gasket under the inlet manifold.

To check this spray 'easy start' around the manifold. If the revs rise you have found the air leak.

[keesiev]

Thanks for the info. I will check it out.
Do you think, this could cause the bogging down and lean mixture (to much air in relation to fuel) the engine is running on?

[Boosted LS1]

^ Exactly.

[keesiev]

Great help!!!
I will check and repair if it is leaking... I is a pitty I did not ask it sooner. Because of the bad performance of my engine I decided not to take part at the trackday at zolder, as it would only depress me being the slowest of the lot...