I have an 04 g35 giving me a few problems. It sounds horrible and has almost absolutely no acceleration. I know for a fact there is an exhaust leak/hole from the rusting which makes the car louder. The exhaust is making a loud popping noise because of the leak but i'm also getting two p0300 misfire codes. All the lights on the dash are on and I have done multiple ECU resets. She idles rough and won't really accelerate. Also, the spark plugs have just been changed. Any help would be greatly appreciated. Heeeeeeeeellllllllppppppp!
Ill try to get a video of the sound and acceleration tomorrow. Thanks in advance.
My uncle thinks it has something to do with the timing.

 

Check your cats

 

My fault I meant to mention, that's what they originally told me was wrong with the car. I was told the cats where clogged, So then I got test pipes. They are on.

 

Is the car tune?

 

i have the same problem in my 03 g35 she idles rough but when you give it a little gas in neutral it smooths out as soon as u try to drive with a load in it it starts again i changes all of the plugs and hollowed out both cats

 

Because that will make it run so much better...

 

it does a lot better as does for my 335

 

Had a P0300 error code. Changed out my spark plugs and coils. After replacing still had the misfire rough engine idling. Found connectors on cylinder 4 and 6 were not seated all the way. Problem resolved, all good now! Just have to be careful to not mix up your ignition coil cables. I recommend doing one cylinder at a time vs. removing everything all at once. I also recommend marking each old part with a Sharpie and mark which cylinder it came from. Now I have to reset my service engine message.

 

These wire marker booklets work great for auto use, the adhesive doesn't crap out over years of use and they're easy to apply, just pick a number or letter and wrap it around the wire.

https://www.amazon.com/ScotchCode-Pre-Printed-Wire-Marker-Book/dp/B07DK64ST9