98 F-150 with 4.6
Sounds like I have an exhaust leak when driving vehicle.
When idling, I cann't hear it.
Have checked exhaust and can not find leak.
Think it might be a cracked exhaust manifold or gasket leaking.
How do I check & pinpoint.
Removing exhaust manifold appears to be a pain. Any tricks??
Thanks

 

Sounds like you may have the dreaded broken manifold studs. As best as you can see, look around where the manifold meets the head and look for black soot caused by an exhaust leak.

 

As you look at the manifold, look for a missing bolt. Probably one of the ones towards the back. If you have this, replace all the bolts on that side since you will probably break one or two when the header is pulled.