Dovegabanna,
Are you saying that the vacuum hose that had come loose was in the air inlet tube that connects the air filter to the throttle body? My nephew's wife's car seems to have the same symptoms you described - pretty noticeable shudder/bucking under very light acceleration at highway speeds (light enough to cause acceleration, but NOT shift the transmission down a gear), but no problems under full throttle or at idle. Does my description sound like what you were experiencing?

David