Hi. I had a k and n air filter fitted to my fiesta. I recently got the software update to improve starting which this worked but now it is more noticeable when the engine is warm coming up to a round about or just slowing down in general the engine revs struggle n most of the time cuts out.
I have recently put the standard air box back on but unfortunately have broken my foot so unable to test it. My dad took it out and said the engine revs did drop but didn't cut out so I have to wait and see when I can drive again.
I didn't know if there was a common fault with fitting a air filter like this?