Way to tell if CSC has been changed?

DEpointfive0

You can check the trans bokts to see if they have been fiddled with, that's about it.

But unless the previous owner was on the forum, the odds it has a HD one is slim to none. IMO, you should buy one from Joe @ ZSpeed and install it or hold it until yours breaks

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Two things. First, if the CSC was replaced with the stock OEM unit, you will still have a "ticking time bomb". As you've already gathered, the stock units are prone to failure. Second, if the CSC was replaced with the Z Speed HD CSC, it should be obvious from an inspection of the clutch lines running out of the transmission housing. Go to the Z Speed website, and look at the photo of the HD CSC and clutch lines. The lines are braided stainless-steel and distinct from the factory lines and set-up. Even the bleeder valve is different. Then take a look at the lines running from your housing, and you should know right away if you're running with the stock CSC or the HD CSC. Z1 has a CSC replacement unit that could have been installed (?), but it is an entirely different set-up than the stock CSC. It would be obvious through a quick inspection if the Z1 unit was installed. Again, if in doubt simply take a look at the photo posted in the Z1 website and compare. Trust this helps.