can anyone help a friend of mine, hes a owner of a evo 3 and the other day he started it up and there was a almighty bang/backfire ever since then the car misfires and struggles to rev. hes changed the coil packs, leads, airflow meter , checked crank timing, hes run out of ideas, if anyone has some good advice please e mail me or reply to this post, thanks

Has he changed the spark plugs?
My mitsi did this, I even had flames coming out of the air filter :O Changed the plugs, problem gone