The only "delete" I am aware of on the Crossfire is the aft most catalytic converters (they do not have O2 sensors) and the resonater from the exhaust system of the SRT6.
Most people do that to change the tone of the exhaust system, or simple do not want the added expense of replacing a catalytic converter. I do not think it adds much in the way of performance improvement, perhaps some, but not much.
I've done both on my SRT6, but I do not live in a state that requires smog/safety testing.

I haven't heard of anyone removing the EGR system.

Others have deleted the SKREEM, but that has nothing to do with performance.