One common issue on this engine is the valve seats getting crushed and flattened out and causing the compression to a be a little lower resulting in a misfire under certain loads. The cylinder compression and leak down test will tell you if that head needs to be replaced.

You then need to check and see if the source of the misfire is the lean codes. Low fuel pressure from a clogged filter or weak pump can cause both concerns. leaking intake gaskets or PCV or vacuum hoses can cause both concerns.

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