RE: Pipe cleaning
Unleaded is perfect, remove exhaust from truck, dah, flush out, not much ends up in there a bit of dust/oil build up, bit a black gunky stuff after 5 years or so, LOL, but fuel cleans it straight out, only ever done it once, when a stupid curry eating wasp built a nest in one and blocked it ! Yea boy was he sorry ! Air compressor, and fuel !