94 Cima Brake Booster Question

[RaggedyFool]

Hey all,

This is my first post and question that hopefully some people might have some advice for.
I was driving my Cima the other night and the brakes went stiff and the red waring "!" light went on in the dash along with a deafing sound. My first thought was the booster and I'm thinking that's what it is but want to see your guys thoughts.
I tried to find any vacuum leaks but didn't hear any hissing or anything so I'm not thinking that's it. Looked under the hood and nothing seemed out of place or sounded wrong.
The only thing that's been done to the car prior to me buying it was a z32 conversion on the brakes.

My question is, if there's anything else I can check for or anything I can check for specifically in regards to the z32 conversion that may have been done improperly before I bite the bullet and try to order a booster through Amayama.

Thanks in advance to any and all help.