2003 Mustang gt misfire.
I've had this GT for about a year now and ever since I've had it, it's had a misfire. At first I noticed the crank pulley wobble back and forth and as I read previous articles it showed me that low end under drive pulleys could do that and cause a misfire. So I went ahead and purchased the under drive pulleys from steeda. When I first installed them the car stopped shaking and didn't feel like it had a misfire. About a week later it started shaking all over again. I've busted my head trying to figure this out but just can't. Some guy told me that it was a gear behind the crank pulley and when you put crappy udp it ruins it so it throws the timing off. Anybody know what he could be talking about and is it hard to do? He says it's pricy to replace due to his hour wage is 95 dollars per hour and he'll need about 6 hours. Please help!