Adding duration to the exhaust side by opening the valve earlier is far more effective at increasing exhaust flow than leaving the valve open later and increasing overlap. Therefore N20 cams are usually ground with a wide centerline angles and then are run in an advanced position to put the intake lobe back where it likes to be for maximum torque which also has the effect of opening the exhaust valve sooner. These types of cams also work well on non-nitrous engines that have less than optimum exhaust system specs, whether it's poor port flow, catalytic converters, or shorty headers and full length street exhaust systems.