Last Weds I was coming back from Birmingham City Centre at 5.30pm (anyone who knows this time knows how bad the traffic is!), it was 30 degrees and I pulled over at the petrol station. When I got in I started the car with the door open and heard a noise, it sounded periodical, like rotational type noise (think of how a big end knock sounds, but it wasn't a knock), I gave it a light accelerator pedal and it got faster with revs, it sounded like back of engine / underneath driver. I then nursed it home as I was only a few minutes away. Had a nosey and couldn't hear it clearly with engine running (no one around to rev so I can hear it). I left it then went in and didn't start it until morning. The noise was not present, I got to work, no noise again. Then I drove to the gym after work, again peak traffic (bloody Birmingham), the noise was back! There is no loss in power and it feels like over certain revs it goes away (like the flow increases enough to no longer escape so easily?) but then again so many other noises appear like wind noise, tyre noise so it is drowned out. I was away the weekend in London so car stayed at the gf's place, when I got in and started it, I definitely heard exhaust leaking noise from under the drivers area of the car. Could this sound be the manifold, either the flange or the flexis? When the flexis / flange leaks what kind of noises have people heard? Of course I am paranoid as hell thinking it is the big end bearings that have gone, but then I watch vids / experience of other peoples cars that have had them gone, noise isn't the same, but still doesn't help the paranoia haha. Thanks in advance.