Well.. I'd say you probably disturbed something when you were working on it.. That's the most likely..haha.. Was the filter really dirty, could it be running correctly now(and high because someone had wound the idle up to compensate for poor running)? Have you tried slowing the idle ? Could you have routed/pulled the throttle cable out so it's sticking where it fits into the carb, or perhaps you've knocked a vacuum hose off, or the choke isn't returned right in because the cable is snagged somewhere ? Are you are sure it was the fuel line and filter you changed(some of those have a restrictive/one way valve that looks a bit like a fuel filter, but it's on a vacuum hose to the tap..,