Any other ideas?

 

O.k. I get it on the 93 octane (couple gals. during or around the Seafoam). Back to the plugs. Were they Motorcraft stock (ni-chrom plated copper cores) or Plats? There should be a permanent sticker under your hood (mines on the top of the air filter houseing) w/ pertanent tune up info.: base time set, Gap, recommended Motorcraft plug. I'm guessing it says to use a M/C Plat plug @ .044. Now for the stock non-Plat plug, Motorcraft recommends for your your 94' 302 ci (N- type), a gap of .054. Personally I go for the larger spark Kernel of the copper core gap (insured by a higher output coil). So we're back to what Plug & gap! Although if your Coil is weak, Neither plug, correctly gapped or not, will give you optimum ignition. 100K miles implies it's output could be wanting. dr bowtie agree's that the coil is the most probable cause. However, we have to make this assumption on less that adequate information. We have to assume the base time is correct & there are no outstanding Error codes either active or in continuous memory (which there probably is), because it's a mystery to you, also! If you are unable to furnish any more information and you want to bet on the coil, this would be a good time to upgrade the whole Ignition system: http://fullsizebronco.com/forum/show...ht=timing+bump