If your vehicle is showing strong smell of raw, unburned gasoline from the tailpipe, here are the most likely causes and the parts you'll need to fix each one.
Worn spark plugs or failing ignition coils prevent the air-fuel mixture from igniting in one or more cylinders. The unburned gasoline is then pumped directly out through the exhaust system.
A degraded oxygen sensor can falsely report a lean condition (too much air) to the engine computer. The computer compensates by dumping excess fuel into the engine, causing a rich exhaust smell.
A dirty or mechanically failed fuel injector can leak raw fuel into the cylinder even when it should be closed. This creates a severely rich condition that the engine cannot fully burn.
The MAF sensor measures incoming air. If it is dirty or failing, it can overestimate the amount of air entering the engine, causing the computer to inject too much fuel.
If this sensor fails and constantly reads cold, the engine computer will stay in 'warm-up' mode, continuously injecting a rich fuel mixture as if the engine is freezing cold.
A failed mechanical fuel pressure regulator can allow fuel pressure to spike, or its internal diaphragm can rupture, sucking raw fuel directly into the intake manifold through the vacuum line.