What Juanky said!

When we talk about vacuum leak it means that air gets into the intake rather than out of it. It matters because the MAF sensor does not account for this extra air therefore it runs lean and causes misfires.

Fix this air intake hose first, then look for more vacuum leaks including the rubber hoses that connect to the intake system. Even the brake booster hose.

There are many ways to check. Look at some Youtubes on finding vacuum leaks.