right now my car isnt running and i just noticed that my bac valve hose is cracked, bad.2 questions is this possibly why it wont start and should the hose be hard plastic btw i have and 87 t2 completely stock

There's a couple hoses. Is it the coolant line or the air line from the air intake funnel? Air line should be a basic soft rubber hose and the coolant line should be a rubber and mesh high temperature reinforced piece. You can just go to the store and buy a couple feet of 3/8" fuel line and use that. Couple dollars. You can use any old hose for the BAC air lines as long as it seats snugly with no air leaks.

It can cause a major vacuum leak if it's damaged. If you remove the BAC your idle needs to be bumped up a few RPM.

My BAC to "air intake funnel" was hard plastic (or hardened 20 year old rubber) and was cracked. I used some silicone hose but it didnt seal well. I expect it was a primary cause of my tuning problems.

The silicone vacuum line line kit I'd bought included the black hose and the silver silicone hose to assemble a tight fitting replacement.

it was the one to the air funnel it was also hardened i have got some hose to replace it now and will let you know how it goes