Hello everyone, i've had an very annoying exhaust leak. The engine is louder than usual and you can hear it leaking out under load, sounds a bit like pinging but happens at all rpm. anyway you can hear hissing etc. when the car is sitting.

anyway i have been frigging around with the front to rear flange, but it doesn't seem to be that, it actually sounds a bit closer to the engine, so i suppose the next place to look is the manifold to front pipe flange. Anyway I was wondering could a leak before the O2 sensor stuff up your idle quality etc. by throwing the reading out.