Mt 07 stalling at idle

[Donmo]

when I start my 2017 mt 07 , first it runs for about 30 second and goes off when idle , but when I am moving it moves fine while I am throttling but immediately I lift my hand off the throttle it jacks like it’s going to off , also when I try to slow down to make a u turn or over take , it stalls and it doesn’t turn on till after 4 to 5 tries . I don’t know what might have caused the problem, I have checked the plug , the fuel pump works fine , someone said it might be the 02 sensor since I changed the exhaust to M4. Thanks for your help