"PVC is resistant to many alcohols, fats, oils and aromatic free petrol. It is also resistant to most common corroding agents including inorganic acids, alkalis and salts. However, PVC should not be used with esters, ketones, ethers and aromatic or chlorinated hydrocarbons. PVC will absorb these substances and this will lead to swelling and a reduction in tensile strength"
This is what I found before building mine, sounds good enough.
I don't expect it to last forever, probably will last like rubber hoses would, but I expect to get my moneys worth out of it. People have used PVC intakes for years on other types of engines.
If you want something that will outlast you, it would need to be metal. My next manifold will be of the vw alumninum center section and stainless steel grab bar type, but I couldn't afford that right now, its over $100 in parts to make one of them. Even with them you'll have rubber couplers and gaskets somewhere usually, which will need replacing at some point.