89 3VZE idles rough lacks power
 

I have a Toyota 1-ton-truck-based RV with the original 3VZE engine and manual transmission, 73K miles since new. The engine is running rough at idle and really lacks power at all but red line torque. I have just replaced the plugs/wires/cap/rotor. I find that when I remove one wire at a time I get an excellent spark on all six, but the engine does not change sound when cylinders 3 & 5 are removed like it does for the other four, so those two cylinders are the likely location of the problem. My dealer mechanic (who recommended the ignition component change) had checked the compression in those two cylinders and reported it was good. I get no check engine light.

What are my next steps?

OK, Found the culprit. First I rechecked the mechanic's work on compressions; > 160 psi all around, good stuff. Next I bit the bullet and dug down to the injectors. The two suspect cylinders' injectors were packed with fine rust silt and completely blocked (A Toyota Coronary Infarction) :banger:

This probably stems from a tank of awful gas I got in Mexico last summer. It brought the RV to its knees and I changed out the fuel filter at that time; all seemed fine after that, but having sat all this winter I guess more worked its way past the new fuel filter, or perhaps just moved itself along to where it could do more damage.

So here are my followup questions:

1) Should I replace the fuel filter once again? Is one brand better than another?

2) How about the in-tank fuel pump screen filter?

3) Should I try to clean out the fuel lines and if so how?

I've ordered a set of four-hole injectors, and valve cover gaskets while I was at it; since I'm in this deep I might as well check the valve clearance too.