I replaced the harmonic balancer on my girlfriends 2007 Mustang after the pulley flew off while breaking the CKP sensor on the way. I replaced both and it runs just fine but is a relearn needed? I've been reading about the relearns but I can't find anything pertaining to this model mustang. Since it runs fine I'm not too worried about it, but I thought I'd ask you guys. A little bit of further info: at first it was very hard to start. After I finally got it to start there was some valve tapping for about 5 minutes probably because it sat for almost a week. After that it ran just as good as before.