Welcome here, could you please tell which country you living in and what trouble your XC is giving you exactely, for in EU are different standards for emissions, etc.
Muffler: increased noise when hot might be a lose catalyzer, hard to fix but possible
Corrosion: depends very much on first owner and NON rust proofing in a SALTY state.
If uou are really unhappy with your ride try to give it back.
