On boost = yes. On na? Only if your car likes to run on soap and water

 

A vacuum guage. Period. You can go to Sears and buy a $25 Mity Vac kit which will allow you to test vacuum and apply vacuum (great for testing solenoids) and it will also make bleeding brakes a breeze. You can test vacuum both idle, part-throttle, and WOT. The test is simple. Attach the gauge to the nipple coming off the passenger front of the upper intake manifold. Note the vacuum at idle (should be a rock steady 18-20hg). Next, have someone apply throttle at a very steady rate. The vacuum will rise and will stabilze around 26hg, maybe even higher. Finally, have the person push the rpms to around 2500rpms and then hit the throttle. The vacuum should drop like an anvil and then quickly recover once they release the pedal.

Another test would be to route the line into the cabin and drive around and watch the vacuum.

A DIYer, should not be without a vacuum gauge. It can tell you so much about the running condition of you car and is far easier than taking guesses as to if there is or isn't a problem.

 

awesome info Dave. I'll be looking to buy one.