I bought a truck once that had just had the valve springs replaced and would not quiet down, turns out they had installed the rocker shafts wrong and no oil was getting to the lifters.

When you run an MDS engine with just the plastic plugs in it will shut off those 4 cylinders and it will have 4 cyl power but the lifters will not be noisy.

I am not causing global warming, I am just trying to hold off a impending Ice Age!