Move to Senegal ruined exhaust system

[AfricaXterra]

Dear enthusiasts, I appeal to any advice you may have. I moved to Senegal (West Africa) with the American Embassy and shipped by great 2007 Xterra. All my paperwork required me to remove the catalytic converters because only leaded fuel was available. Upon my arrival in country, I found out they just switched to unleaded fuel, so I wasted my time and money. Too late.

I removed the catalytic converters (including 2 attached to manifold) with Midas. Standard muffler could not handle increased flow, so purchased a performance muffler. Had it replaced here, but still have a loud scratching sound everytime I rev the engine too much. I feel a drag with the car, and am concerned I might be causing damage. Mechanics here are great with chewing gum and fabricating parts out of nothing, but don't trust to play with my exhaust system anymore. I think reinstalling oxygen monitors that were removed might help, but how to install?!? I can order parts and have them shipped here, no problem, but need some real advice on this. I've been offroading on sand and hope it hasn't been getting into the system.

PLEASE HELP!!

[OffroadX]

What 02 sensors did you remove? The 2 closest to the engine are required for the engine to even run. The ones further downstream are just there to ensure the cats are doing their job properly and trip a code if not.

[AfricaXterra]

The O2 sensors removed were along next to the catalytic converters that were removed. Midas removed them thinking it would trigger issues because of using leaded fuel. I think my best bet is to get some O2 sensors, since they left the holes there for them. I recently found out there is a Nissan dealership here, so I "think" they may be able to fix the issue using some new O2 sensors that would be hooked into the electrical system. Do you think this might be the solution?

Will check spare tire pressure, but how is that relevant to the exhaust?