Hmm... I am wondering what your compression psi are? On my 1998 I wouldn't shift down to the floor. I just tighten the shift down cable by about 1/8 to 1/4 tighter then it's original position. Fixed my issue. As I think the cable slowly stretch.

If your loosing mpg and power. I am thinking possible fuel injectors not clean. Lower compression caused by valves needing adjusted.

As if your head gaskets are good and your not loosing psi through the head gaskets. These engines are not noted for rings going bad. Leaves head gaskets, injectors and valves out of adjustment as possibilities.

If the compression psi is testing out decent it would rule out head gasket especially if you did a leak down test.

I wouldn't expect spark plugs and wires as that mostly shows up as misfire issues.

If all is checking out good. I verify you pcv valve isn't stuck.

I think by observing other users these engines really should have their valves adjusted before 300k miles. Or at least verified the valves are all in spec around 300k miles.

If our valves are not opening fully and closing properly, I could definitely see the mpg going down and major power loss occurring.

These are just thoughts of possibilities of what could be issues. Naturally, it maybe something totally different.



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