Assuming you are talking about the turbo hoses I think you will find they are silicon anyway, just plain black rather than bright colours. I tried all types of pipe on a 200tdi conversion and they all failed until i fitted silicon. (Originals had been dumped by the breaker and I was not paying LR prices) Coolant pipes are a different matter, vsrious grades available. I have just bought EPDM for an awkward job on a VW van.