Misfire at 4.5 to 5 thousand RPM

[ionod]

Hi,
I recently changed my battery for a new one. I have since noticed that the engine misfires at about 4,5 to 5 thouasnd RPM while revving engine in park, not yet taken it for a run (difficult to give it a burst through central London) Any ideas what It might be? No faults have come up.

Thanks