Mitsujunker..Welcome to the world of Mitsubishi and ticking lifters.
The whole topic of Mitsu's ticking tappets is discussed in depth at DSM.COM and other Mitsubishi websites that I peruse. I think the nature of the problem is that the lifter sits on the valve stem and the heat conducted simply cooks the oil inside of the very small high pressure chamber within the lifter.
End result? Dino oils eventually lead to gunk that restricts the tiny orifice which allows it to pressurize with oil. This then traps air inside leading to the dreaded tick.
I just bought an '02 Lancer with the 2.0L (4G94) engine. I did my first oil change at 1k and sure enough it was ticking immediately. However, I bought the factory service manuals - there's a procedure to purge the air that can get trapped in part of the lifter after an oil change or if your oil gets low. Sure enough, no more ticking.
However, you've probably got dirt or other gunk in the lifter if you've used conventional oil for a sustained time after the overhaul. I think a high quality Synthetic would tend to clean these deposits out, but not as fast as Auto-RX. Mobil1 w/SS 10W-30 would probably be a nice replacement oil that's more readily available than Amsoil or Redline, but I like all your brand choices for synth oil.
FWIW, I wouldn't run 10W-40 in our Mitsu's, you're just wasting gas mileage and horsepower on friction. Unless you're autocrossing the car at a track, stick with a high quality 10W-30 weight oil.
In regards to your plugs and carbon problems. What octane rating of gasoline have you / are you using? On evolution.net(a Lancer forum), I've seen pictures of plugs from members that insist on running 93 octane from day one. The plugs pulled at mileages as low as 8k look as if they're covered in a thick black layer of diesel soot with some oil. As someone else posted, it'd probably be a good idea if you cleaned up the combustion chamber before doing the Auto-RX treatment.
I prefer Redline products SI-1 Fuel System Cleaner that you can find at PepBoys. Someone posted on another thread that Redline can be harmful for plastic and/or seals in the fuel system, but since it's recommended by BMW dealers, and heavily diluted in gasoline, it's okay by me.
I used it on three gassers in our family and it has smoothed out the idle and eliminated rough spots on a 106k Volvo850, a 13k 4Runner, and my 2k Lancer.
If you are or have been running high octane gasoline, I would stop this practice once you complete your total clean up procedure. Run the lowest octane rating of gasoline that does not cause constant pinging or knocking, but not below any ratings specified in your owner's manual. For Mitsu's it should be 87, which is what I run.
Please PM me if you need the lifter bleeding procedure. I can copy it out of the shop manual and send it to you.