Can't see an LED bulb during the day???
Please share the bulb type or part number. I'm thinking you purchased a poor or perhaps low output bulb. Superbrightleds.com sells different levels of brightness, and the level I purchased for my f150's parking lights could just about pass for a headlight!
Adding in the resister...because you were preventing the fast blink? If so, was it a resister they provided, or did you install one yourself? What was the rating of the resistor? I went the route of installing a LED flasher; this way I can install a conventional filament bulb or LED without the use of a load resistor.
It is better to keep your mouth closed and let people think you are a fool than to open it and remove all doubt.