We have a Holley 600 cfm model 4160 carb on a Chevy 350. Am having a problem with gas leaking into the secondarys after the engine is shut down. Bought a kit and replaced everything in it to no avail. I am stumped with this one. This thing has an eletric fuel pump running about 6 lbs and until the pressure guage reads 0 the problem persists. Any ideas???