I am an entry level mechanic and trying to help a friend with their Subaru. So they had cylinder misfires on 2, 4, and 6. I just replaced their crankshaft pulley because of a wobble and the pulley was staring to dig into the timing cover (Saw metal flakes coming from pulley when I gassed it).I was hoping that the balancer may be causing the issue but it was bad anyway so I started with replacing it. Also whenever I snap the throttle shut the car bogs down and in most cases dies. Anytime the foot comes off the gas pedal. Also when I snapped the throttle shut it sounded like a poping noise coming from the air filter... almost like when the valves are bent or otherwise not shutting all the way on the compression stroke causing a little positive pressure. I was thinking maybe timing chain jumped a tooth but then why is it not effecting the other side as well? Was also thinking VVT but forgot to look if this engine was equipped with VVT or not. Any ideas on a path for diagnosis?