In reality you should have taken action 2 years ago.the brakes were under spec. the inspecting mechanic said that they should never have passed a safety inspection. I get the feeling that the people on this site aren't really trying to help but instead just like trying to make other people feel stupid
If the statues of limitations for small claims has not run out , you could try and sue for the cost of repair for those defects , if you can show the court the cost.
Filing fees are small and the time you spend on it.
You can try adding the converter and arguing it ,but this is a recent event and they can argue anything could have happened with it within the 2 years.