is your cat bad? I mean, it has no impact on anything unless it's clogged up.
The EGR also doesn't hurt anything as long as it's working ok. but I won't argue against removing it.
the charcoal canister absorbs the fumes given off by the tank when it warms up and the gasses inside expand (and then the engine sucks the fumes out of the charcoal while it's running). the only truck I owned that came with the canister removed smelled like gasoline on hot/still days.