Someone help

lol
I've had my VTR 2 weeks tomorrow and it flew through it's MOT 2 weeks today, theres absolutely nothing on the test sheet to say theres anything wrong with it but...
Over the past week or so, when I'm driving especially in 5th gear it makes a horrible whining noise, sounds a bit like a helicopter lol!
I don't know if you can hear it from the outside but from the inside as a driver or passenger it makes my exhaust sound crappy!
It's almost as if my exhaust is blowing but it's worse than that.
My mate claims it could be the gearbox about to bost but surely it wouldn't have flew through it's MOT if this is the case?
It is quite hard to get it in to 2nd gear and also first, but every other one is okay..
And it only whines when I accelerate not when I put my clutch down or anything else..
Any ideas what it might be?
Thanks xxx