Sorry, posted this in the wrong room at first...

Easy all, i've got a new noise coming from my engine...

It sounds like some one knockin on the front door lol, but constantly!

Gets louder and more frequent with revs, mostly in neutral, 1st & 2nd, but not in 4th?

Im chargin my fone up now so i can get a video of the noise, but thought someone might have an idea without a vid.

Incidently, i have filled it with 99 octane fuel since i got it, but i filled it with 95 the other day now it does this - Coincidence?