My 98 super 8 is currently having an air fuel issue that causes it to rough idle, shut down and lose power, I suspect it may have something to do with the vacuum leak. I recently took my exhaust manifold off and bought a donut gasket, my ranger doesn't have cats, do I still need the donut gasket? My header connects ditectly to the pipe and I think it's leaking from that connection

 

Welcome to the forum

No such thing as a dumb question, but there are dumb answers aplenty, lol

What is a "super 8"?

1998 Ranger 4cyl was the 2.5l SOHC Lima engine, I assume you have that because this is the forum for 4cyl(I4) engines

Pretty much all fuel injected engines use an Air Valve to set idle levels, Ford calls theirs the IAC(idle air control) Valve, it will be located near the throttle plate, to by pass it
Find your IAC Valve
After engine temp is warmed up, let engine Idle and unplug the 2 wire connector on the IAC Valve
Idle should drop to 500 or so, or engine may even stall, either is good, it means no vacuum leaks.

Most Rangers didn't use an exhaust "donut", exhaust manifold had a cone shaped end that sealed against flare shaped exhaust pipe when they were clamped together
An exhaust leak between the engine and O2 sensor will cause a False Lean on the O2 sensor so computer will be running the engine Richer than it needs to, so a drop in MPG
Pull out a spark plug and see if tip looks like Rich burn, i.e. darker brownish color, a very light brown is normal

You should have TWO coil packs
Engine should start and run with either coil pack unplugged, 3 wire plug on the side of coil pack
Try it
BOTH spark plugs in each cylinder fire at the same time, there is no alternating, so engine can run fine with either coil pack off-line
Two coil packs and Dual spark plugs are used for better power, simple as that, no its not for emissions either, lol
If engine runs the same on one coil pack, but not at all on the other then you found a problem, check those spark plugs and swap the coil packs around, if problem flows coil pack then get a new one to replace that one.

When did you get gasoline last?
Could you have gotten some "bad gas", gasoline with too much water in it?
Water is heavier than gasoline and settles to the bottom of the tank over time and this causes similar symptoms