I'm using one of our member's unfortunate experience here as a warning because I've heard rust on various EVOs may be common on the IVs/Vs at least.
I've also seen a few examples privately and publicly of sellers who send their EVOs to auction with serious, but well hidden rust damage.
http://forums.jdmvip.com/Augustines_...VO-6134-t-3#29
When the owner wants to hide it usually they'll paint black over the whole underbody/main areas of rust and even use undercoating. A good Exporter who inspects the car on a lift will get the hint that "it's too clean" and look carefully and normally find it and can put in a claim, return the car to auction at the seller's expense AFAIK. But companies who only offer "Straight to port RO/RO service" can't and won't be able to do this, and even more-so they may notice it but turn a blind-eye to it (too much hassle for some Exporters) so buyer beware especially if you are going for a model with known rust issues.
It's also possible that this is from accident damage in the rear that is not repaired well. I'm not sure, but it seems with cases like these happening with EVOs it's worth mentioning.
If anyone has more info about this and what other EVOs suffer from this/why then please post here too.
I hope this helps prospective EVO buyers and hope no one else gets one of these hidden rust examples because they're costly to fix or may not be road-worthy in some cases.