Hi.there thanks for your reply
Ok..Ive actually got NGK's 2014 List for all sparkplugs and lists all the Fabia 2 models - Its a pity you couldnt actually see the old plugs as this would of confirmed wether it was the wrong plugs or not,and whos in the wrong here..What i can say is though that the plugs you have there pictured and the code i see there ( ZFR6T-11G ) "are not listed" for that engine you have -
If the Dealer has confirmed your engine is a "Engine code CAVE" which is the 1.4, 4 cylinder, 132kw...... Then that uses a very different plug - The Plug that should of been in there and listed as such is ( PZFR6R8EG )
Skoda,VAG Part numbers spark plug 'longlife' = 03C905601A / 03C905601B (NGK - PZFR6R8EG)
The CHFA the dealer mentions is the 1.2, 3cylinder 44kw engine.......
The differance between those plugs is the heat rating and the Gap..the ones you have there in your picture has a plug gap of about 1,1 where as the plugs that should of been in the engine have plug gap of 0,8 - so the differance is plain to see - too wider gap! on the plugs you have there in the picture / wrong plug and would likely of been contributery factor in the excess carbon fouling within the engine - the white deposits
I can give you a copy of the sparkplug list i have to see for yourself if required..but clearly as far as i can see i would be inclined to agree with the Dealer here that the plugs are indeed the wrong type for that engine you have in your car..and they may have gone by the standard 1.4 63Kw engine that uses these ZFR6T-11G plugs....I do hope this helps..If you require to ask anything further then just continue before you rate