Fuel system

It is not common in regular passenger vehicles. This is more common on race applications or off road vehicles. Basically what happens is when the fuel heats up and returns the tank it can actually increase the temp of the fuel. When this happens there is a chemical reaction or change and the fuel will start to create a vapor lock in the rail.

Your vehicle has a return fuel system so this is possible. What is the detail about the issue and we can try to figure out what the issue is.

The way to solve the vapor lock is to add insulators for the rail. They are pretty common on the internet.

So do you still have the lean codes since you found 50 PSI? Have you checked the engine over for vacuum leaks? I assume that is how you found the intake gaskets but clearly lean on both banks is most likely unmetered air coming in.

https://www.2carpros.com/articles/repair-lean-mixture-codes-p0171-or-p0174-on-some-manufacturers

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge