Floods out fuel pump is fine intake gaskets have been replaced can it be a fuel pressure regulator

If the fuel pump is replaced and the pressure is still too high, then the issue may be with the fuel pressure regulator. The fuel pressure regulator is responsible for controlling the fuel pressure in the fuel system. If the pressure is too high, then the fuel will flood the engine and cause it to stall. You may need to replace the fuel pressure regulator or adjust it to the correct pressure.

This sounds like a leaking fuel pressure regulator so as soon as you turn the engine off the fuel leaks into the intake and floods the engine, locate the fuel pressure regulator and remove the vacuum hose then cycle the ignition switch to run the fuel pump and watch the regulator nipple for fuel. I hope this helps. Take care.

If you are getting Fuel in the vacuum line, it sounds like you could have a bad fuel pressure regulator. Check the line that comes off the Fuel pressure regulator. use a hand vacuum pump see if fuel is being pulled out of the regulator.Replace regulator if you find fuel
coming from that vacuum port.

Check the fuel pressure. It will tell you if the pump, fuel filter, and fuel pressure regulator are all good. Fuel pressure is critical on fuel injected engines.

Check your spark plugs for wear or the wrong gap.

Another possibility is a vacuum or air leak. Check all vacuum hoses and the intake manifold gasket. The GM 3.8L engine is prone to lower intake manifold gasket failures. Sometimes the upper intake gasket, too.

LOOK ON THE FUEL INJECTORS RAIL YOU SHOULD SEE A BLACK CAP THAT LOOK LIKE A TIRE AIR PRESSURE STEM REMOVE THE CAP AND FUEL PRESSURE REGULATOR IS THERE

If it acts like it is flooding while idling, but it runs fine on the road, it could be running too rich and flooding it out due to leaking injectors, bad fuel pressure regulator, or excessive fuel pressure.

I would start by replacing the Fuel Pressure Regulator since it doesn't cost as much as the injectors.
Check your fuel pressure using a Fuel Pressure Check Gauge to see if the fuel pressure regulator is maintaining the proper pressure.

Vacuum is attached to the Fuel Pressure Regulator to control system pressure. When the fuel pressure regulator is not functioning properly it causes the fuel pressure to be above normal operating pressure. This condition causes excess fuel to be injected causing a rich mixture that produces black smoke.

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

I just replaced the fuel pressure regulator and now I am hearing a vibrating noise from the fuel line under the truck. What do you think the problem is.

the most common cause of this is the fuel pressure regulator.

The fuel pressure regulator may be failing. If your engine code is "W" the regulator is under the upper intake manifold. You may replace the entire injector package or just the regulator.

DORMAN regulator Part # 55162 about $40
ACDELCO CPI injector Part # 2171431 about $400

These parts may last slightly more that a year if you are lucky. I carry an extra regulator and manifold gasket at all times.

I have had similar problems and had to replace the fuel pressure regulator. It's a major expense because it sets below the diaphram in the intake manifold. Ask your mechanic about it, it may be the issue. I would get about 30,000 miles between replacement, I've replace it 3 times since purchasing the 2000 chevy blazer new, first one was under warranty.