I got the car in october last year and haven’t done anything to the engine except a cobb accessport and a muffler and resonator delete. Ive been running a stage 1 that doesn’t require any mods And i flat foot shifted at 6.5k rpms i say about 10-15 times.The day after, i got white smoke on a cold start and i took it to subaru and they said my oil was running low so i did an oil change. I also got a check engine light and i read the code(cylinder 4 misfire). My DAM is inconsistent and i get feedback knock all the way up to -11.80. I deleted the code thinking it was like a one time thing but i got a misfire today again. The roughness in cylinder is not doing good either. Is this a possibility of bad spark plug, fuel injectors, or ringland failure? The car has 8.5k miles on it and still has warranty.