Why does my 1990 Buick Lesabre die all of a sudden?

i have a 1990 buick lesabre with a 3.8 liter engine. i first noticed the problem when my car died all of a sudden when i got up to speed. i pulled over and tried to start my car again and it had a terrible miss and i heard popping in my engine. the exaust manifold was glowing red hot. i eliminated the catalytic converter and that solved the exaust manifold problem. my car still dies when stopped at a stop light or when i get up to speed. and when i start it again it either wont start or it has a terrible miss and the popping comes back. it gets worse when i give it some gas and then it dies again. i have replaced the O2 sensor, cam sensor, EGR valve, spark plug wires, coil pack, and the crankshaft sensor. none of these have fixed the problem.