What makes a car spit gas out of tailpipe?

Defective coolant temperature sensor, oxygen sensors and a leaky injectors and overpressurized system

A defective coolant temp sensor will not cause that problem, neither will defective oxygen sensors. To figure out which injectors are defective you must remove all spark plugs and the distributor cap. Cycle the ignition key twice, then try to start vehicle. The compression from the piston will shove the gas out of the spark plug hole on whichever cylinder has said defective injector. You people are of no help, but please post this for others to see.

Since you have thrown all these parts at it, surely you have some scan tool sensor data to analyze. What are you seeing? What did your injector balance test tell you?

The vehicle in question (not mine) had never so much as had a tune up with 130k on the clock. It's called preventative maintenance. Cylinders 2,4 & 6 were not firing correctly in the first place. A new distributor fixed that problem. The intake manifold gaskets commonly leak and the knock sensors are garbage as well. These engines are junk when new in particular the emissions and ignition systems.
If I was throwing parts at it I would have replaced O2 sensors, a mass air flow meter and a TPS sensor as well. 99% of "techs" would have been lost anyway, there was NO CEL and all of you guys need an OBD code to fix anything at the stealership.