need to replace exhaust sensor on a 04 fiat punto 1.2 thinking of doing it myself but was told today by a mechanic that when it replace it has to be re tune by a computer, but looking on youtube this guy shows how simple it is to replace a exhaust sensor and he didn't mention anything about retuning it with a computer, also got a 08 peugeot 308 1.4 with the exact same prolem, so who's right can anyone tell me. thanks.