Threre is an EGR valve that joins the intake manifold to the exhaust manifold. It's purpose is to mix a little exhaust gas into the intake to reduce pollution. When it isn't working properly, the ECU can cut turbo boost or restrict airflow by opening the wastegate and closing the ARV, which is another valve on the side of the crossover pipe. So that's what all of this stuff is supposed to do.

The advantage of removing it all is that a simpler control system is less problem prone.

The disadvantage is that you will have a car that pollutes more and is technically illegal for road use. If your state were to mandate an effective inspection program, you can be fined and your car would have to be removed from the road until you put everything back.

There are a lot of moving parts involved in this system...the ARV, EGR valve, two vacuum transducers, the ECU, lots of connectors and vacuum hose. The problem may be as simple as a leaky vacuum hose, or one of the major components may be malfunctioning. Opinions may vary, but I think it's always easier to fix the system as designed. Some believe that there are performance advantages to removing the pollution controls, but that isn't the case. When everything is working correctly, there's very little impact on performance or fuel economy.