I've never had an 8300HD that didn't work if you adjusted the IR output on the MRF-300.
It sounds more like emitter placement is wrong. Take a bright flashlight and shine it through the front of the unit and look for the IR receiver and make sure you have the emitter stuck right over the top of it then play with the IR emitter level until it works.
There are 10 types of people in this world, There are those who understand binary, and those who don't!
