egr and petrol sleeve

Hi, just typed a long thread only to be told need to log in again,
Anyway here goes

Something has got me thinking for a few days now,
With software we do a egr delete, what does that mean,

Let me explain, the egr itself still works, the real egr, where the egr thermostat fits on,
Water still flows in it, and exhause gas pushes into it,
Now in a normal car the gas flows from outlet manifold into egr and then goes into that small pipe and into the air intake thing where the intercooler pipe fits, there is a small valve thing which I assume is what is deactivated so the egr gas does not enter into it,

Now if the gas is being pushed into the egr, surely that pessure must release somewhere now, how much pressure can it hold and won't it give up sooner by keeping this pressure. The gas is entering but not exiting,

Next question,

I am looking at fitting a cover pipe for the petrol breather, apparently it is a common problem on my car, 2005 to 2007 models,
Where did u buy it, etc,

Thanks,