[A26B]

Reversion flow occurs primarily in high rpm engine decel. It's not very common in that i have only encountered 3 or 4 customers (that I know of) with catalyst reversion damage. It destroys liners, pistons & rings. 90~92 model style manifold/cat are more susceptible due to the close proximity of the cat. I have posted a photo below.

If you anticipate road course type driving where engine decel braking is common, then you could eliminate that concern by installing headers and eliminating the cats altogether.

I am not aware of any late (93~95) catalyst reversion damage. Moving the cats further aft. The early (90~92) manifolds were discontinued with the 93~95 models, which were offered as direct replacements. I am not certain, but would imagine late style heat shields would also be needed.

I don't think it is anything to get overly concerned about for the vast majority of ZR-1 drivers.

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