As for the metal pipe creating a different high than a glass one or other devices.. id assume it is purely speculative. Human beings have an inbuilt part of thier thought process that allows them to physically experience things because they believe them, not because they are real. This is the basis of the placebo effect, and many tipes of psychosis.

What im saying is that the old guy probably just believes the metal pipe gives him a better high, and since he genuinely believes it, for him, it does.