Good data in the thread and exactly what I was saying.
2 ½” 8221; Inlet/Outlet Flowmaster ( 2 Chamber) 249 CFM
2 ½” 8221; Inlet Outlet Flowmaster ( 3 Chamber) 229 CFM
2 1/2" Inlet/Outlet Magnaflow 284 CFM
MagnaFlow has 20% more flow than either of the Flowmaster configurations.
It also produced a little more peak HP. The dynamic range wasn’t tested, but it’s likely a larger differential at lower RPM.
Magnaflow 372.8 HP
Flowmaster 369.4 Hp
