max A/C air flow setting being distributed to other vents

I believe that there is a vacuum leak or the hvac (vacuum controlled) panel mode door actuator isn't working properly. I tend to lean towards a vacuum hose leak or hose disconnected somewhere but where is it is the 64 thousand dollar question. Any ideas where a good place to start troubleshooting would be?? I don't have any fancy tools ie smoke unit etc so I'm at a disadvantage there I hoping someone could point me in the best direction to fix this problem! Thanks