I removed both the EGR and SAI on my X30 when I fitted the later 3.2 exhaust manifolds which don't use it.
I turned a small stepped bung to fit the EGR valve, and secured it with the nut cut off the now redundant connecting pipe; this was less work than making a blanking plate between the valve and the inlet plenum. You can completely remove the valve if you replace it with a cheater circuit so the ECU thinks it's still there, I intended to do this, but never got around to it.
Similarly, deleting the SAI requires the actuating solenoid(on the radiator, near the battery) to remain connected electrically only; everything else can go in the bin, which removes a lot of clutter at the front of the engine. This requires blanking the exhaust manifolds which is slightly more work than just plugging the tubes, but it is well worth doing. There's a large air filter box in front of the NSF wheel which you can also remove.
If you're keeping the original manifolds, there's no point in buggering about with the EGR. The SAI is slightly more worthwhile as it makes servicing the front of the engine much easier, and both the pump and oneway valve do fail occasionally.
There are no noticable performance gains of any sort from removing either system.