[luiscompean]

After installing bbk long tube headers and bbk high flow performance xpipe on my 07 mustang gt the check engine light came on and the p0300 and p0302 dtc codes came up now I know the cylinder two is suppose to be misfiring and maybe another cylinder also but all this happened tight after I installed the headers Nd xpipe. Does anyone know what could be causing this issue? And does anyone know how to check if the o2 sensors are working properly? I also have installed ford racing performance spark plugs. Any help and/or advices will be greatly appreciated