Can someone please tell me where I can find the metering jet or sometimes called the fuel line restrictor that goes on or in the inlet to the dual carbs on my 98 GTX? Also the diagram shows there should be a check valve on the fuel return line. I have searched tirelessly on the web and cannot find these parts. What role do they play and how important are they but most importantly where can I find them for purchase since I would like to bring my carbs back to factory specs. Thank you for your consideration