DamianLT1

replaced. How much power loss if any would this cause?

D James

if it leaks after the o'2s then your not gonna cause much problems, if before you could cause alot. If the sensors are bad then yes performance will suffer since they are sending the wrong info to the computer, I wouldn't replace them unless i knew they were bad for sure or you have lots of miles, typically they can last 60-100,000 miles, if your in that range I would have them checked out. I have a header leak at the flange before sensors and its not causing any problems yet, but I think i'm lucky and its not bad enough as of yet. They are expensive at about 50 bucks each.