Hi SK, Without getting too far OT, (ie the thread was not really about comparing HKS 3040 to a GCG Hybrid)
The GCG turbo I had (I was told) was good for way more than 250 rwkw. The hight level specs follow (don't know the details sorry, and this is a combination of what I saw and what I was told - as stated before, I am not an expert on turbos)
GCG - TO4e front housing 0.70 AR - Garret 3040 core, Bored & ported VG30 rear housing - bigger integral wastgatel and bigger exhaust. The manifold was a GCG tubular mid/low mount. We could not get any more than 250 rwkw out of it.
With everything else the same - just take off the GCG and put on the HKS top mount manifold and HKS3040 (1.12 rear AR) 330 rwkw - no problems. Oh - Trust type R 45 mm eternal wastegate too.
Now I realise that this is probablly not really a fair comparison - as I went from a internal gate to an external gate.
GCG did offer to change the turbine blades as they thought it was the problem - But I didn't have time to do R&D on my turbo and car - so I opted for a known brand and model - I haven't heard of too many un satisfied HKS owners - But when it comes to home grown hybrids and hi flows - you really have to put your trust in the supply chain.