I have a Chevy Lumina and my car is not starting regularly. It always starts but after I give it a ton of gas and rev it up. I changed the spark plugs, tested the fuel pressure and its not the fuel pump. Almost everything is original in the car and it has 97,000 miles. Any suggestions or somewhere to start?

Welcome to AF, not clear here, you have to step on the gas to start it or to keep it running you step on the gas?

If I just turn the key to start the car almost 90% of the time it will not start. Therefore, while turning the key I have to press on the gas and then the car finally fires up. This problem only occurs when starting the car not while driving it.

It is possible the throttle body is dirty as well as the idle air control, both should be cleaned for step one.

got any error codes?

Does the fuel pressure hold after you turned the key but didn't start the
engine? The pump should work for 5 sec, build the pressure and then switch off.
The pressure should hold. If it doesn't then there's a leak in injector(s)
or in pressure regulator.

In both cases you'll get a rich gas-air mixture and "gas pedal down" only helps to
correct it back to a "normal" one.

Does this problem occur @ hot start or cold start or both?

Both times sometimes I wont run it for a couple days get in and it start right up. Then other times I will shut it off grab some food come back out and it has trouble starting again.

let me repeat my questions:

1) do you hear the working pump sound for the first 5 seconds after you
turned the key?
( if you are not sure then you may ask someone to sit in the rear near the tank and listen)

2) you can buy the fuel pressure gauge at $22 online, attach it to the
fuel rail and check what's going on with the fuel pressure - this will give you a lot of information. If you don't want to buy or rent the tool you may
take some stuff to collect the spilled gasoline (use caution!), put it under the end of the fuel rail and slightly depress the valve on the port to check if the pressure builds up in the fuel rail.

3) check if there's a gasoline leak to the vacuum pipe that goes from the intake to the fuel pressure regulator.

4) check if the fuel pressure regulator works properly (read Haynes for that).

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You can also start from the spark - remove the spark plugs, check them,
test the spark, look at the wires when it's dark if there's a discharge, and so on.

But I suspect it's something with the fuel supply. Does the exhaust
smell with gas when you finally start the engine?