Have a look at these plugs

Just a few observations and comments.
1. When lead was taken out of gas, the reading of plugs is not readily possible.
2. Your pictures are horrible. Looking down in the plug provides useful information.
3. The plugs look dirty on the insulators, so they have been in awhile. Dirty insulators leads to loss of spark energy.
4. At least 3 have fouling, the gaps appear tight on those. What is your gap setting, they look tight?
5. You may have weak ignition, vacuum leaks and other mechanical issues resulting in imbalance . I am saying that because they differ. Is it a TBI system?
6. Tuning EFI without AFR is rediculous.