Turbo off. Not sure if the Turboservice company can measure the air flow before/after with the billet wheel installed. They are gonna balance it on and take a look at my 5 year old turbo. It looked in very good shape when i took it off. No shaftplay, no damages to any wheels. Hope it will last for more years. For a fwd street car that are not driven so much on the freeway, the GT35R is very good. If I lived next to the highway, it would felt a little short..