Did anyone ever solve this problem? Im having nearly identical issues with my 83 zx 2+2, slight intermitent puff at idol, then radical popping (backfire?) under initial exeleration, and no pooping at cruise unless im in fifth. The pop is only noticable under light load, ie granny driving, if i get on it it doesn't do it, at least not as bad. The last bastion of hope i have is in my vavles, it sounds like a diesel, would that cause this?
edit: non turbo, stock motor, new intake/manifold gasket