P51-302, welcome!
i like your thinking. i agree, especially with C, A, D and F
just cuz your CEL is not on, does not mean that there are not codes stored in the KAM. check them.
as said, the ECT and lambdas can read within spec, but not correct for the situation (i.e., ECT says motor is cold when it is warm). this will not trip a code, since the sensor reads within spec, but not correct for the situation (in this example a warm motor). leads to overly rich
the other thought i have is that you said you cleaned your
K & N a month ago. if you liberally oiled it, the excess oil can and will travel upstream and coat the MAF wire. that can cause your problems.
i would swap plugs, cap and rotor. they are cheap and important. people do stupid things when it comes to plug choice and gapping and such. plug wires are more expensive, so i would recommend ohming them out before buying new (unless your pocket is smoldering with green smoke.
good luck.