Do I need to contact an outside party for help with a manufacturer dodging a warranty?

I Recently purchased a vehicle still covered under the manufacturers warranty. The engine did experience an event, but the dealership stated things that were untrue and when taken to another dealership and followed up with an outside shop it was verified to be untrue. I am now experiencing unrelated mechanical issues that the dealership is saying are not covered because of the mistruths that were previously noted in maintenance notes. I have gone to corporate toyota with no avail.