Replacing an OEM diverter valve is, in my opinion, not a modification.
Yes, a piston-type valve (such as revision d) performs better than a diaphragm-type valve, but it's not a shiny Forge aftermarket part, is it...? It's OEM.
Some VW dealers are sh1t, revision D part number is 06H 145 710 D. Price ~£50.
Do it - I'm standard, and even I noticed more whooshes, pops and seemingly more consistent boost. Or it might be a placebo effect.