I have a 68 gto that I bought a couple of months ago. It is stock with a 70 quadrajet that's got me puzzled. The thing idles really rich (black smoke) and off idle it bogs and backfires unless you slowly bring up the throttle. My idle screws are around 1 1/2 out and the float level is good. The carb has been rebuilt twice, once before I bought it and once after I bought it. All internals look new and clean. Now hear comes the screwy part... if I turn the idle screws all the way in the engine cleans up and STILL RUNS! Also, if I crack the secondaries manually by themselves it has instant response with no issues. Anytime the primaries are involved it bogs and backfires. When I shut it down, almost instantly gas leaks from both sides around the primary rod onto the intake. I assume it almost empties the bowl because it takes alot of cranking to start it after it sits for awhile. When I had it apart and filled the bowl with fuel it did not leak. I suspected too much fuel pressure but under test it was under 7psi. Oh and casting plugs have been epoxied. Any ideas?