Ok, so yesterday I gave in and had my GT on the rolling road courtesy of Reidy Remaps. I went for economy over performance. Before the remap I had a route I'd covered many times and that always returned 50-51 MPG. I did the same route today and achieved 56 MPG, not bad. At lease half the trip was on dual carriageway at 70 MPH. I also did my trip to work and back on B roads and achieved average of 65 MPG!
However, we did have a couple of problems, firstly the clutch, it slips if he increased torque above 280 lb/ft! So that was reduced a little, but will obviously have to be done at some point. The second was that the turbo was "spiking", he did his best to resolve this, but said it was likely caused by the turbo's variable veins being coked up. He seemed very knowledgeable, and I'm sure he knows what he was talking about, he said he's going to look into it and get back to me. Has anyone had this turbo "spiking" before, and if so what was done to resolve it?