1993 Taurus Sho 3.2 Won't Start

I have a '93 Taurus Sho 3.2 Automatic. Within the last month I started getting intermittent poor idle and performance problems along with an occasional hard starting issue. When the car acts up the tach shows abnormally low rpm's but when it comes out of it, it is like a switch and returns to normal instantly. Now, the car won't fire at all. It cranks with the sound like it is off time. I have replaced the plugs and wires, coil pack, ignition module, battery and cables, throttle position sensor and ignition switch. I have double and triple checked that the plug wires are right and nothing is unplugged and all the fuses are good. The no-start issue happened right after I replaced the plugs and wires and it was acting like I had them in the wrong position but I know they are right. The engine is definately getting gas. Help!!! Crank sensor? Computer?