Doesn't appear to be either the injectors or the spark...

I listened to the injectors and all clicked normally.

I checked the injector resistance, and all ranged from 13.3-14.1 ohms.

I pulled all 4 plugs, and they had normal burn corrosion on them. I cleaned em all up, checked the gaps (one of them had too big of a gap), and put them back in. Also looked for cracks, and didn't find any.

I checked the plug wire resistance, and all of them measured good. Didn't have a spare set to swap them out completely though.

When changing the oil pan, the oil smelled gassy. The coolant level is also low. Would a compression check tell anything about the head gasket, and could this be a source of the problem?