Re: 99 f150 4.6
"Only a misfire on two cylinders"! White smoke!!
The engine has two cam chains and two, one for each, cam chain tensioners.
The whine is probably the least of your problems. You have an intake manifold coolant leak into a cylinder(s), or a blown head gasket, which probably is the cause of the misfire code. But #2 and #8 are different cylinder banks. Are you loosing coolant? Do you have water in your oil?
It's probably time to pull the engine and fix (rebuild the engine?) the problems before you do any more damage, but first do as Cat said. Plugs always have a story to tell. Or, you can just hang in there. You still have six cylinders left.
(Don't do that!)