Bostech # MP5153 Fuel Injector

1. Remove the air box, unless you have already upgraded your air intake system, then this step is not necessary. If you will be installing a supercharger with it, remove the air inlet temperature sensor as well. They tend to stick a little, so be patient with it.
2. Take out the bolts holding the strut tower brace on and remove it. These bolts are generally 10 mm in size and there will be eight or so of them. A standard 10 mm torque wrench should do the trick. If they stick, use a little engine cleaner to help loosen them.
3. Continue removing components until you reach the fuel rail. These components will include: idle air control valve, EGR, throttle position sensor, throttle cable, EGR valve, intake manifold, all hoses, electrical connectors, fuel lines and, alas, the fuel rail which houses the fuel injectors.
4. Wiggle the fuel injectors off much like when replacing spark plugs and wires. Each one will spray some gas, so no smoking during this process. Place the new injector in place of the old on and lubricate the O-ring with some 20W engine oil. Reinstall everything and you are done.

If you're getting raw fuel to exhaust pipe:

1. Check for open intake valves.
2. (Bad pressure regulator)  It builds too much pressure in the fuel rails and consumes a large amount of excess gasoline.  Also, ½ gallon of fuel ends up in the oil pan.  In this case, the oil should be changed immediately.

If you're getting raw fuel to exhaust pipe on early Vortec 4.3L engines:

1. Plastic fuel lines that connect the injector’s fuel housing to the metal fuel supply should be replaced with the injector assembly to prevent engine flooding, oil contamination, and engine stall.  Reference GM CPI nut kit, Bostech Part Number 55163.
2. Fuel in the exhaust pipe could be a symptom of a leak in the fuel pressure regulator.
3. Poppits on spray nozzle could be stuck open if the area they connect to is not clean and debris contaminates the spray tips.

To find the fuel leak:

1. Remove upper intake manifold
2. Turn the key on (but do not attempt to start the vehicle)
3. After the fuel pump comes on, you should be able to visually identify any leaks.