This happened to my friends car a couple of years ago, he sent the head out to Metric Motors and they removed the plugs, and checked everything over. They also replaced all the valve steam seals and I think all the intake valves were found to be out of spec and replaced. Since it had 200k miles on it he told them to go through it and just replace what was needed. I forget what he paid but it worked quite well the car runs better than ever.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200