No.
If you still have stock downpipes with a GT-R then you will still have a set of cats on the vehicle and will not get the gasoline smell when pulling up to a light or when the vehicle is cold and in the fuel enrichment stage. Nissan from the factory was a major FAIL in the design of the stock Mid-Pipe on the GT-R. It is VERY heavy, has 2 more cats that are not even monitored by the ECU and also a HUGE resonator, more like a muffler.