The silicone bits vary wildly in price from peanuts to loads of dosh depending on size / angle. Your average 'turbo' size 90' bend is about £15 I suppose.
The best way to make a turbo hose is to use as few elbows as possible and to make up the distances with solid ( metal / plastic ) tube - as is done on most production vehicles if you look.
Aluminium joiners are available with rolled beads on the ends to help sealing but at turbo pressure just a straight cut off pipe and a decent wormclip will hold the pressure with no leaks.
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