CBR600f dies when idle

Hope it's ok to ask for help here, I'm at a loss after much googling and diagnosing.

This started happening last week, I'll be riding my 2003 CBR600f and waiting at a red light and the bike just dies. Also, when starting up it seems to struggle, I have to hold the button in for several seconds of chugging before it catches and fires up.

First thing I thought was it's a battery issue, the battery is either old (it was) or charging isn't working somehow.

I bought a brand new battery and put it in today. Starting issue is still the same, and it still dies already on the first red light.

So I can rule out charging issues like stator and reg/rec right?

What else can cause this? Maybe bad plugs?