1995 GMC Suburban running poor

After initial startup idols well, turn off then restart and it floods, black smoke, will run if left alone but if you give it gas it will want to die. It will run an idol fine eventually but if you turn it off and try to restart, same thing happens and gets worse when it up to full operating temp. New fuel pump, new FPR, new plugs, hand code 54 we cleared it it has not comeback in about an 1/2 hr of run time. Any idea

Thanks, Tom