This one of my newest products. 4.5"-3" straight reducer couple  or  3"-4.5" straight reducer couple 4-ply reinforced silicone. All Black NO Logos
Unlike rubber hose, silicone will not spoil with age and is highly resistant to hardening while maintaining very good compression characteristics.
Working Pressure: 70 psi - BAR 4.8
Burst Pressure: 207 psi - BAR 14.3
UV and Ozone resistant
Handles high boost pressures, high temp
Higher flow and better lubricity then rubber
-76° up to 356° Fahrenheit Operating Range
Very good compression characteristics This great for custom turbo and supercharger systems. This is the size needed for all 05-09 Mustang GT throttle bodies.

Item can be purchased at

http://byoracing.com/item/to-straight-reducer?t=modal-em