Need help diagnosing change in rev pattern

Hi all
Yesterday my 2004 TD5 started changing its rev pattern. It seems fine when I first start it up for the day but once the engine is warm it starts to sound a little off beat. Once it has started it doesn't get back to the normal rev pattern unless I turn off the engine and start it up again, it then takes around 30 seconds to revert back to the weird off beat pattern.

It's a little hard to describe so here is a video I recorded so you can heard what I mean:

My friend suggested it could be a bad fuel injector and to try using Wynns injector cleaner for a few tanks of fuel, but I am interested if anyone else has any other opinions?

Hi yes looks like a Injector might be to blame, or a failty fuel pump

For anyone who has the same problem, and comes across this thread, the issue ended up being caused by the injector wiring loom. It had corroded and got oil in the connectors, so it was acting up. Seems to be a common problem with TD5s, so that's fun. I also had an error code for a faulty MAF sensor so i replaced that. I don't think that really had much to do with my problem, but who knows!