[A26B]

Matt,

A cost-nothing test.

One of the tests that will expose a weak spark problem is to put the engine under load at a low rpm, usually in 6th gear from about 45~50 mph & gradually accelerate. Very much like you described. Weak spark miss is disguised at higher rpm, although it does affect engine performance significantly.

I suggest that you re-visit coils & wires. Pull the plug wire from one plug at a time, install an old plug in the wire and lay it on the plenum. Start the engine & gradually pull the plug away to cause the spark to jump. A blue spark about 3/4" long is good. If you have an orange spark, it's weak.

It's best to do this in the shade to see the spark better. Note the spark condition of each cylinder. Having weak spark on one cylinder only does not necessarily rule out a coil.

I also recommend using silicone grease (dielectric) on each end of the plug wire boot and on the coil terminal. They seal better and resist moisture better which can also cause a miss.