Please explain how to check for vacuum at the brake booster itself?
Start the engine and remove the large vacuum hose at the booster, check the hose first to see if it has collapsed while running, if it has replace the hose.
An easy check is to hold the palm of your hand over the end and feel if it is sucked in. If not, replace the hose first and then look at the Booster.
Search Ford Thunderbird Questions
Ford Thunderbird Experts