What year did they change the PCV valve tube on the 2.5L? On my 84, the PCV valve is right at the elbow on the valve cover, where on my 86, the PCV valve is by the throttle body. On my 86, it looks like it is not leaking, or leaking very slowly, and looks like a better setup.
If a new grommet does not work, then I would look at getting a PCV system from a 86 (possibly 85) 2.5L, from the valve cover to the TB. They use the same PCV valve.
Details on my Fiero here
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