2001 Ford F-150 vaccum leaks

Your best bet would be to purchase a vaccume gauge (10 to 100 dollars depending on quality) and check your system yourself. Most of these will have instructions with you that describe how to run the different tests and what they mean.

Alternatively, vacuum problems can be difficult to find, but usually are easy to fix. Check all of your vaccum lines coming from your throttle body that go to different parts of the car. Listen for a whoosing sound. Look for any cracks or dried lines. Esspecially look at the joints and connection fittings. Inspect the air intake system to make sure there are no leaks in that system. With your mileage, it is likely dried up and cracked vaccum lines. You could probably replace them all of less then 40 bucks.