Courtenay Sport Garrett Conversion. The brief was to achieve 420bhp with Garrett GT3071 turbo, tubular manifold, 76mm exhaust, 80mm air flow meter, 630cc injectors and Courtenay Sport Full Height Intercooler. The 80mm Astra VXR is maxxed out at around 420bhp so the achieved figure was the best achievable using the given components.