This was posted on a similar thread a few weeks back, following this allowed me to change the id
Originally posted by duff77
You need to open your gt5 save into bruteforce and press set PARAM.SFO as Template and select use current PARAM.SFO. Then open the save I uploaded and double click PARAM.SFO. This will open the PARAM.SFO Editor. Account ID box should be blank so click Account ID... button this will put your account details into box. Click save and it will ask to overwrite click yes to everything. Close the editor and the press update account and copy PARAMS select yes to everything again and that should work.