Only time a bigger exhaust will make an engine lose power in any part of the torque curve is if the header you are using does not suit your engine,the only thing it will do is make noise with a bigger than needed setup for the street.I have always found after tuning more Honda's than I care to remember that as a rule of thumb these sizes work best for street cars
1600 to 1800cc 60 to 65mm exhausts noise levels can be controlled without killing power by restrictive mufflers
1800 to 2000 +cc 65 to 75mm exhausts moderate noise levels and very good power levels.