Turbo Charger Kit VG30Dett using G25-550 really like what GCG have done taking the more efficient g series and adapted the gt rear housing using the common method of intake adaptors to make a bolt big power small frame bolt on kit. Now Im not saying 550+550 makes this an 1100 horsepower kit, I would calculate more like gt2871r power with better spool less chance of compressor surge, you may even get gt3071r power with huge boost 35psi plus, its really not hard to see this setup as a game changer, I would say GCG would make you a 660 if you asked and you could be looking at gt3071r/gt3076r power levels in a bolt on kit. The v band 5 bolt housing are on market as above which can be taken out to 60mm 55mm so if you take a g30 frame 3" intake supercore there is no reason you cant make a g30 660/g30 770 bolt on kit that takes up the room on a gt30 and makes gt35 power levels in a bolt kit, now yes it will lag (i hate that word) but I'm talking deep into the 9's and looks stock which is hilarious. I'm not saying this is the best way run these turbos 3" / 4" intakes, external wastegates, 3.5" outlet turbines is but hey its possible.
I hope GCG did some test fitment here as I can tell you now this WILL NOT FIT as a bolt on unless they also changed the compressor housing which basically would kill the top end flow of these and the efficiency. myself and 2 other US builds are running g25-550/660 turbos externally gated on custom manifolds and documented the fitment issues as did Dane over USA on the factory manifold.
