banging

Hey guys, Here's a strange one. I was on a trackday a few weeks ago and after a few sessions I started hearing a popping sound from under the tank on my 03 RSVR, especially when trying to drive out of the slower corners - it was like I had no real throttle control at low revs, just on or off...

I think I've got a real problem. When my Mille is in neutral I can feel and hear something banging/knocking inside the engine. If I click it into first the knocking disappears. Anyone got any ideas? Gearbox? I'm gutted, the bike's been so good for ages but now this. :(