did you check the spray pattern on your injectors when you had them out? did you clean them? old k-jet injectors are notorious for problems like this, also haveyou checked your fuel pressures. check control and line pressure, maybe you have a bad warm up regulator. some models have a series of vacuum hoses and a check valve on the warm up regulator that act as an accelerator pump when its cold if those hoses are cracked or the check valve is bad it also could cause this problem.