its no doubt that.. there is a piece of metal that is moving back and fourth.. with little numbers... wich i am guessing is something to do with timeing.. so it is the harmonic balancer
yes thats it, i read your other thread, if it is shaking the car the rubber has probably came partially out of the balancer, go buy a balancer puller(special tool for pulling it off) and pull the thing off and check the rubber in the balancer, these motors are notorious for doing that, i dont believe the stock balancers are very good on them.
this is a front view of a balancer it is a solid unit..the rubber ring can be seen. this is what gives way and causes the outter ring to slip which causes the vibration..if this balancer is not a solid unit its bad and needs to be replaced..
rear view of the balancer you can see the rubber cracking and that is the reason i replaced it before it failed..