Hi all,
I fitted the second hand MAF sensor last weekend and it seems to have cured the nasty juddering at low speeds but didnt cure the flat spot when acccelerating hard. I managed to get the garage I bought the car from to pay for a diagnostics test at our local Nissan garage (£40 ish plus vat) and they said everything was fine, not one fault code, bought new air and fuel filters so gonna try them and see if this might fix it. will keep you posted.