I have a 2007 mustang GT V8- previous owner installed JBA exhaust system and cams. Engine light came on and car didn’t pass emissions rest (required in my state) so I brought it into ford. Said the problem was the exhaust system so they replaced the whole thing (sadly). Now it runs really rough and the Engine light didn’t turn off. They think the previous owner installed cams which is causing it to run rough. I’m a newbie but I want to figure out how to fix it in my own. Any advice on what...

Cams timing wrong