My car surges and ive tried alot of things already. I can tell you for sure there are no vacuum leaks and the ignition system is perfect and egr is blocked off. I think there are air bubbles coming through my fuel lines because if you listen close to the return and feed lines you hear a noise that sounds like when you turn the key and the fuel pump primes. It sounds like something rushing through the lines but you hear it off and on, its not a smooth consistent sound. When I check the fuel pressure and i release the pressure I see the bubbles in the drain hose. what could cause this?