Re: 98 2.5 missing and then it doesn't
If the EGR thing doesn't pan out (indeed, those are nothing but a headache, and you can get plates to cover up where they went), you could test the ICM (ignition control module— when those go stupid they cause all kinds of problems and after a couple of decades they just go...happened in my Fairmont Futura awhile back), you could also test the coil packs. They aren't infallible and intermittent spark should be traced back there logically.
FOR EXAMPLE: If on a distributor system, a plug isn't firing or has intermittent spark, you test the plug, test the wire, then the distributor cap, then the rotor, then the points or hallway effect switch and then the flyweights. The condensor should be looked at, too.
So why wouldn't you trace ignition problems back to the coil pack?
I'd go plugs, wires, coil packs, ICM...check all electrical connections, grease up with non-corrosive afterwords, etc.
I've have more than one coil pack go stupid on me over the years. Just my two cents, and it's suffering from inflation. :P
'91 Ranger, 2.3L 4-Banger knocking out 140 HP. Plopped the head out of '94 and an RV cam in it. 2WD, zero options. But, I love her to death.
Avatar is when I drove up the Bohemia mining saddle in Oregon, a fairly well-known 4WD trail around here.