Another fuel system restriction, aside from fuel line sizing, is this fuel strainer in Holley 1850/4150/4160 carburetors. Remove it for best results. Just make sure you have good fuel filtration that is also 3/8 inch. Also, keep fuel inlet sizing in mind. If your entire fuel system is 3/8 inch, yet the fuel inlet is 5/16 inch, you have only 5/16 inch, which defeats the purpose of 3/8-inch fuel line. Make sure the carburetor inlet is at least 3/8 inch.