Bleedski, the diverter valve you mention (going to smog pump/air injection pump) is not a valve that has anything to do with the turbocharger, rather, it directs air to the catalytic converter and so forth.
The turbocharger diverter valve is located in the stock, secondary intake manifold . . . if the seals are bad, it can leak air and the engine might idle and/or run rough due to an overly rich condition (air metering assembly thinks more air is needed than really is = rich), and you will hear a fairly loud, metallic "thunk" sound when you suddenly close the throttle (like throttle blipping at a stand still). I suppose the diverter valve piston could be stuck in its bore, but I'm not sure that would show as increased lag.
Below is a thread on the diverter valve that will help you ID it . .
http://forums.pelicanparts.com/porsche-911-technical-forum/71370-changing-930-dump-gaskets-pictures-galore.html