Doing my shift servos today and noticed that when I shut the truck off, and immediately pull the dipstick, a ton of air gets sucked in, like theres a vacuum in the crankcase. Also sucks air through the dipstick hole while running. Is this normal for an engine? If not, what could be wrong?

 

what you are talking about is normal, it is the pcv(positive crankcase venalation) valve pulling the fumes out of the crankcase and puting them into the intake. it is a good thing, helps your oil last longer.