Brake pedal valve

[Chamberpains]

That's what I was guessing because its the hardest 1 to replace.
Hopefully you took a picture of the line positions before you did the job and marked which line went where as you took them off. They are incredibly easy to mix up when you work in that tight of an area.

Also check your relay valves aren't shot or gummed up. One should be just in front or under the front of your 5th wheel.
It should look something like this though not exactly.