850 t5 p1 maf probs with numbers and wont run/pull right

hi all got a pulling problem with my t5 p1 engine start runs fuels and boosts and dosent misfire or miss etc no faults codes are flying but as the turbo comes in it only pulls slow thew the rev range unlike it used to do , so after rechecking pipes,vacum ,boost etc and fuel ,pressure the engine seems spot on till the maf went down and ran like apig ,so this is the queery i bought a nice maf off a nice chap off here fitted it and bingo no fault codes and runs and dosent overfuel but this is the only thing i can think off so heres some numbers ive checked of both mafs old maf has got 0 280 217 107(3 507 697)bosch but stamped on the neck were the mafs bolted inplace its stamped (469 08 3b) new maf says 0 280 217 107 (1 275 749) bosch but on the neck as (589 09 1a) i know they say i only need this number 0 280 217 107 ,but as u can see the other set 2 last sets of numbers are differnert and im sure this maybe my problem?? can anyone explain this to me ,as when im asking for for 850 t5 mafs p1 they only use 0 280 217 107??? for refferance

MAF details 

Hi Powernut, The 3507697 number is the one that come up in the PDF parts catalogue on the Volvo owners club site and also in VADIS. I am on the verge of getting a new MAF from an E-bay company quoting this exact number. I also have checked all hoses, idle air and so on, the only thing that I think I will also change is the engine temp sensor under the thermostat as I was advised in a post that these fail intermittently. That said I do feel I have been going round in circles.