2000 magnum

Downstream o2s
Monitor emissions only. They dont affect mileage or performance.
Check your fuel pressure too.
Not sure how its regulated,but the older ones were a returnless system and if reg goes bad and pushes pressure up, mileage and performance go down. Mind you, it would give you a rich condition.
Low pressure will drive injector pulse time up.
Nother thing to look at is
Coolant temp sensor.
160,000 is low to warrant a new timing chain,the one i just did a chain on had just under 300,000 KM’s on it and chain wasnt bad.
Seen worse. Changed it as timing cover was leaking.