1999 chevy silverado truck will start first thing in the morning, but then has problems starting the rest of the day. Sounds and smells flooded too. Starts best when its very cold outside.

if your smelling gas then it sounds like an ignition problem or timing, could be something in the distributor, coil, or plugs worn out. if this has the corvette motor in it with the distributor mounted at the front of the motor behind the water pump they are known for distributor problems.

Sounds like you aint getting no spark, spark plugs or cap is what I would check.

Check with the dealer, there is a recall on that for software.

Have you checked the fuel pressure regulator to see if its leaking?

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yikes. sounds like you've blown the head. $$$

Sounds like a faulty fuel pressure regulator.Pull the vacuum line off the fuel pressure regulator.If fuel runs out of it replace the regulator.

have fuel pressure regulator or pump checked out

TRY FUEL FILTER IF U HAVENT YET

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.

perform a fuel pressure test at the fuel pressure port.
if is low pressure remove the fuel tank and check return pressure line clips conections