Hi everyone. 1985 LE manual w/ 240,000

I changed my spark plugs, rotor, cap, & wires about a year ago. I've slowly been losing power and now my exhaust is popping and it smells much more exhausty lately. It is not a rotten egg smell. Since losing power, I've changed my fuel filter. No change. I tested my ignition coil and it was out of spec, so I replace that. No change. I held my Cat up to the sun and could see light, but there is some white buildup on the catalyst. I'm thinking it is still good for a bit. I see or hear no vacuum leaks. My intake boot is fairly new.

I checked compression and it was 173, 179,175, 176. Looks good! While checking the compression, i noticed that cylinder 2's plug was much much cleaner than the others. I would consider the others "normal" and the clean one abnormally clean.

Any tips on what could cause a clean plug? Would the cause give me the symptoms described above? My van barely makes it up hills now and feels as if its choking.