Exhaust Question

My friend bought a s10 truck that already had dual flowmasters with no cat(single in dual out). He was wondering which would be louder, running with a cat, or a resonator instead of the cat. The muffler guy said it would be louder with the resonator instead of the cat.

true.
the catalatic converter has a honey comb in it and that restricts the sound somewhat.
a resonator is simular to a glass pack. straight through with tinyholes down the liner.
sound will increase but you will also have a loss of back pressure

He finally decided to go with a magnaflow high flow cat, they claim it is less restrictive than the catco high flows, and a muffler guy I know is doing it for him for $110 out the door tomorrow. Thanks for your help.