Been having both P0171 and P0174 CEL's on the car, with a very rough idle, backfiring (quite fun), performance loss and a weird hiss when I turn the engine off. The hiss may be normal but I've never noticed it before.
Here's the rough idle (it shows the exhaust later on so you can hear it clearer - I have bypass pipes so it's supposed to sound throaty like that, I haven't got a blow in the exhaust!):
https://www.youtube.com/watch?v=3JDbdLx9e4U
And here's the hiss:
https://www.youtube.com/watch?v=o3yYn-_a2Sc
Is that hiss normal? If not, vacuum leak?
I can't see any obvious vacuum leaks in the engine bay. I've ordered two new O2 sensors anyway, but I was hoping I'd see an obvious pipe disconnected in the engine bay. The throttle body pipe was totally loose (I could move it with my hand), but after tightening it, it hasn't made any difference.
Help!
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