revs up while braking

This is a likely vacuum leakage problem.
Check for vacuum leakage at the brake booster and its hoses.

Thanks.

Here is a test from a guide on the site that can help you see whats going on:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

and

https://www.2carpros.com/articles/engine-idles-too-high

Please let us know what happens.

Cheers, Ken