In answer to your question..
OEM or NGK Iridium spark plugs are ok.
Revision G Diverter Valve
Evoms intake if it's numbers and Noise your after.
Save your money , I would bother with different coil packs.
Decat the exhaust and an intake will get you cheaper gains, or budget for a full turbo exhaust either Milltek or BCS or Blueflame in noise is what your after.
If you can find an S3 intercooler , that will give you better midrange over the OEM cooler.
I'm up at RTech tomorrow as it happens