The intercooler pipes are standard and look like they have never been off. They were fabric covered rubber, as you say. The braided pipes (pictured) are from the bottom of the oil tank. I just pictured them as they had oil/dirt on them and I had mentioned misting on the oil tank. I'm hoping it's just from spilled oil. But will clean as best I can and see.
Do you think it's worth getting the other one way valve off and testing it?
As a note, the oil that has been spilled (or leaked) onto the R\H pipe seems to have protected the alloy where it clamps onto the intercooler. On the L/H side there was corrosion where water has been getting between the alloy and rubber. I cleaned it all off and used red rubber grease to prevent it in the future. We'll see if it causes the pipes to blow off now