Help/info needed

[Paul m stevens]

Hi, I have a 09 sti, running a ppp since being in the garage for a power steering fault I ve developed a misfire/heavy pinking just coming on to boost, in first or second gear it revs through fine, but as soon as you load it in the rest of gears it cough and splutter unbelievably, if anyone has any advice or what to look for I would really appreciate it, thanks paul

[savage bulldogs]

Did you have anything else done at the garage ,timing belt ,service ect ?

Have you checked the ECU for any stored fault codes or get a garage to do so would be the first step .