We recommend to install new supply tubes when you install new BBI injectors. The supply tubes have an edge filter inside which has the function to brake all particles bigger than 50µm into smaller pieces to avoid heavy injector failures. Over lifetime the edge filters may have abrassive wear causing particles over 50µm to get into the injector. Also the sealing cone on the tip of the supply tube can show some wear over multiple assembling processes. Leading to leakage between the injector and the supply tube so it is always worth to add supply tubes to your injectors purchase.