Don't thrash it, had the same thing on my first R32 it was a combo of noisy dry bearing and a loose belt, but not loose enough to beat 2 cars in a race driving to the repairer. Lol
End result was advan performance when they were in silverwater removing my timing cover (rookie error) and revving my car even though we'd already established the issue being the dry bearing.
So I got a phone call saying
"something doesn't sound right with your head, it seems to have bent a valve or valves"
Let's just say from that day on I learnt to do everything on my car myself.
Trust nobody unless there considered a friend.
People are shit sometimes and they will have brainfarts that sometimes cost you unnecessary money.
Sorry for the rant but this issue your having and a few others made me how I am today.
Get it looked at ASAP,
Good luck