Is this exhaust for a street engine or race motor? Street engine.... I would be building a full mandrel bent 2 inch ( 51mm ) system with a single muffler! Race motor with 8000rpm rev limit I would up-size the pipe to 2 1/4 ( 57mm ) again build the system with mandrel bends. Stay away from "Push Bent" exhaust systems, They crush the pipe through the bends and rob the system of flow!! Exhaust systems are only as good as its smallest point!! I dont see the need to run a 2 1/2 inch ( 63mm ) exhaust unless you are running the motor to a 9000-10000rpm rev limit all day long eg full race spec engine. If you have a exhaust system that's to big you get what I like to call "Gas stall" that's where there isn't enough velocity in the system to move the gas quick enough and the gas cools down and becomes heavy, This slows the flow down, Exhaust gas moves alot faster when its hot, The quicker you can get the gas out the end of the tailpipe the beter!!


Heres a link to a company who make some good quality mufflers

http://www.flowmastermufflers.com/index.php?page=9