As Alex and I have said. Having a GT28 will make no difference on manifold choice.

As for Blueflame Manifolds, they run too close to the Boost Hose & Slam Panel and causes some extreme heat build up.
Worth avoiding IMO. My mate has one and its melted his slam panel, coz its too close.

I Might be selling my Original FMS Manifold soon all wrapped and ready to go straight onto the car.
Would be looking for around £420 as a COPY of this is available for £500+