May sound dumb, but any time I've had an issue like this it's always been something too simple to even think about.
Plugs gapped?
Relays and fuses good?
No corrosion on plug wires/links?
Haven't happened to hit a fuel cutout lately?
Maybe double check all of your leads and connections with a test light and multimeter.
I know it all sounds dumb, but I've spent weeks trying to find a major problem that's turned out to be something as simple as a plug that wasn't fully connected (true story).