Hi freaks. ​​​​​​

I have a little bit of an issue with my jazz ge si 57000miles 2013. I own this car for a one year and now it starts floating rpms. Car has k&n filter and backbox delete, sensors hasn't been touched. Asked mechanic about it he seen exhaust he can't think of what could be the cause as sensors are intact. Before exhaust backbox delete i use to took out filter and cars rpms didn't dip to stall they where as supposed to be but now it stalls as you can see in video.

https://youtube.com/shorts/J8wyvoIOjoE?feature=share

When driving normally just after cold car light dissapears when in traffic and taking out from 1st gear it dips to 500rpm 10min later i tried to film it doesn't do it at all. Air Filter been cleaned 1month ago with oil applied. Any ideas would be much appreciated.
Thanks all