I have direct ignition. How can I check the suppressors for the right resistance? Which multi-meter from what vendor would you recommend for general testing of cars?

I think the car runs great given the eroded electrode. But new plugs would do be wonders. As far as the fouling characteristics, I don't know whether the 91/87 mix has retarded the timing too much to leave a residue, so I better put in 91 fuel and see how the plugs look after a week. But checking the suppressors would be a good thing, too. I just hope my valve seats aren't going south....