Resonator from Another Car

[iamfaizankhalid]

Assalam-o-Alaikum, I have Honda Civic 1999. I recently found out that it doesn't have a catalytic converter. Instead it has two resonators, which are also from Alto VXR with a smaller diameter (as the exhaust mechanic said).
What should I do? Should I get these replaced?
Should I replace both with resonator or a resonator and a catalytic converter?

[Hassan1991]

Yes replace them. And install the OEM size.

[iamfaizankhalid]

What is the impact of two resonators?
Does resonator in place of cat converter doesn't make much difference in engine performance?
Will it have missing secondary oxygen sensor in this case?

[Hassan1991]

Your car doesn't not came with o2
2 resonators are not the problem, the diameter of them which restricts the flow.
Exhaust has direct effect on the performance of an engine.

[iamfaizankhalid]

That was new for me.

I just found out that my car has a constant Air-Fuel Ratio. Can something be done to make it vary according to different situations (to improve fuel efficiency)?

[Hassan1991]

No don't adjust it with looking at the feedback. For that you need exhaust gas analyser.
Change the exhaust to oem. It is not an expensive stuff to do rather then messing with other stuff.