Rodneym Rod That black material looks like internal partials of rubber hose. I last year went through a problem of fuel pressure and found out that the internal rubber hose has come apart for the ethonal in the gas. I also lost the diapham in the fuel regulator and pressure worked some times or retunred to fuel tank. I don't know how old the lines are in the car but if any rubber is used, you have about 8-10 years. After this time, you can and will get a failure. Gas additives don't help. Not 100% sure on Avigas or race fuel. This is why 5-10 micro fuel filter are so important for a good system. They saved me from cleaning 8 injectors. Did replace all the rubber hoses with stainless, except between fuel pumps and outlets to lines. Good luck ps yellow tape is for
oil and fuel lines. Water is for white tape. sealers are for life, one time on. Rick L.