I'll let others answer about the Cardarine. I consider it a no go since the original manufacturer of the drug stopped clinical trials on it since the animals on it started developing cancer.
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As far as boldenone, I think the reason you're thinking of it for endurance because of the fact it can increase EPO through an increase in red blood cells. But, this is an attribute all AAS have, so it's really not specific to boldenone.
But, you could Equibolan, it's a precursor to a precursor of boldenone. Hi Tech is the only vendor I know who currently makes it. Here's an article about it
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And you can buy it here:
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