I have a 1998 F150 with a 4.2 and manual. I was wondering if it was normal for the truck to be loud, not the exhaust but the intake. It is all stock and sounds as though it is taking a deep breath or having trouble taking in air untill I get into 4th gear. Then it stops sucking in so hard. Is this normal or should I replace the stock air intake with a cold air intake for easier breathing?

 

Sure, in 4th it should calm down.
The throttle body is not open very far.
Has the intake ahead of the mass air sensor been altered or something in the air box been removed?
Hose break etc.
Air filter issue?
You should be able to see it some place.
If there was a problem between the air meter to the throttle body you likely would have a trouble code set.
Good luck.