[HUMTECH]

If it is surging on cold starts and goes away or gets better as it warms up you may have an intake gasket leak. This will usually set lean codes butnot always. Try starting it cold and spray carb cleaner at the intake ports where they mate to the cylinder heads, if the rpm fluctuates the gaskets are leaking. Easier to see if you can monitor fuel trim levels on a scan tool while doing this test.