Hello everyone,
I recently purchased a 2015 lexus gs 350 and strated noticing some weird stuff. Occasionally, when I accelerate slowly I get a brief but noticeable shutter through the car. Could that be my fuel pump going out? Also, I noticing some misfires from time to time while the car is idling.

A failing fuel pump could cause those symptoms, but it's not the most common culprit. Your issues sound more like a standard ignition problem. Start with the simple stuff first. Check and likely replace your spark plugs. Then, inspect the ignition coils for any cracks or damage. A faulty coil is a very common cause of both shuddering and idle misfires.

You can check fuel pressure with a fuel pressure gauge, can rent one from parts store.
no idea what the correct pressure should be, but if its low thats a pretty good bet that the pump is wearing out or the in tank filter is clogged.

Is / was the Check Engine light on? This along with live data on those misfires will help you know where to start the troubleshooting at.

Normally the Toyota Lexus wide Fuel Pump failure will have the car acting like it's running out of gas. Due to the fact that it would be actually be, because it's not pumping the fuel in the tank to the TB. Sound like you need to check, Air filter, MAF clean, Plugs, Coils. Also Intake carbon build up. If it was ignition you should get a check engine light, or have a Pending code within 100 miles give or take of if continuing to do this.

Also no one ever post this with their problem, and no one ever ask which is very important in helping. How many miles on your GS?

Throttle body? Arent all Gen4s direct injected, and as such, it'd be suffering low pressure at the fuel rail?

Not trying to nitpick, just making sure that I'm not mistaken about the FI systems on these.

Yes the GS350 has a TB. Read the Lexus description of the part.

https://parts.lexus.com/p/Lexus__GS-...203031070.html

Also if I am not mistaken Low fuel pressure shows up a s a Check Engine code.

Sure, it has to have a throttle body, but the clarification I'm asking here is that since its direct injected, the fuel lines don't connect to the TB. They connect to fuel rails, and then the injectors, right? Or am I wrong about understanding how these engines are set up?

We're prob getting off topic, but I was simply making sure there wasnt also a connection to the TB. That would be unusual if its connected at the fuel rail

Ok so I may have confused in my post. The point was just as the Lexus TB part says below. Now I understand kind of what you were saying. Even still the TB does have a affect on the fuel delivery and amount of fuel through the ECU mapping on metering the mixture of a/f Fuel delivered, based on the amount of air metered and opening of the TB and measure of Air flowing by the MAF. The TB opening percentage has lots to do with the amount of fuel the Injectors deliver.

Throttle Body - Repair or Replace
"If your Lexus GS 350 is idling rough, has suddenly lost performance or refuses to start, your throttle body could need some attention. Have it inspected or replaced by a professional to keep your Lexus performing as it should."