Good job! I'm glad you are pleased with the results you're getting already. You have made things better for your van - no doubt.I installed S-VCM today. Oh man, wish I’d done it a long time ago. I had the plugs pulled at 101K and that was all the evidence I needed. 3 showed carbon buildup and wet threads, the other three were clean and dry. Now I know exactly where all that oil went...I never had a check engine light, fouled plug, or engine mount problems, but I got sick and tired of filling the crank case, tired of the low rumble with VCM working, and tired of the transmission bucking when cylinders switched on and off. What a crappy system and sloppy engineering...
So, with S-VCM installed and after only a 20 mile test, the van feels a whole lot smoother...like it should have driven all along. I’m a fan of S-VCM, even if a late adopter. I hope at least that I saved our (paid for) van from a premature death.
It's possible that the rings and combustion chambers in the three dirty cylinders (they were the rear bank, weren't they?) will clean themselves up a fair bit just by firing all the time. If you weren't getting misfires or Check Engine lights, it's possible that the fouling is not all that bad. The new spark plugs will help with this for sure. A bottle or two of Techron or Regane through the gas tank can help too.
If it comes to that, you can also try something more drastic like a piston soak using B12 Chemtool or Seafoam or MMO or Amsoil Powerfoam or (insert your favorite additive here).