Running O/R pipe without a tune and you will smell the gas fumes a lot. When I run with my tunes the fumes are hardly existent unless you're revving at stand still. Remember a tune makes your ignition more efficient so it burns most of the fuel inside the engine. Stock ecu settings aren't set up to burn the most fuel, that's why catalytic converters exist, to burn off the gas fumes the OEM settings didn't.
Anyone else confirm my logic? Lol