I think its just a the normal way the nissan and infiniti transmissions work. I guess they will tell you everything is fine.
my G35 was the same way and from what i hear and see peoples car behave the same exact way. Just like how when you get a bit of a slide it will kill the gas and would put your life at risk if your pulling out into the road and its wet on lets say a country HWY. To overcome this, take VDC off
Same thing happens with the transmission. See when you get to 30MPH your car would already be at a very high gear. Then when you want to pass somebody and mash it, it calculated what gear IT thinks it should be in, The more you press the Harder the acceleration would be, Unfortunately the car takes about 2-3 seconds to math it out, Also putting you at risk ( you want to pass them and mash it, they pass you and get in your lane seeing you going normal speed, and out of nowhere you 5-6k deep going 60). I know several of ways to overcome this situation. it is simply computer lag.
Try those methods.
Manaul mode would only truly work if you have the shift pedals. Dont get me wrong, you will still get a decent response with it on and at sport mode. But the pedals have a more direct link to the ECU and therefore you a gain a second. You can confirm with most people and it is a very easy upgrade to do yourself, not very expensive.
Second way is to Get uptune, that would remove some restrictions in the ECU.
From my experience i went to buy a new car this year and wanted to check out the Q50 and to my luck they had a M56s just came in so i went to test drive both. The q50 unforgettably did the same transmission lag as my G. it was so frustrating to find out a 2019 car still had a lag like a 2007.. i test drove the M and i have to say that it felt much smoother and the response was way way better, probably due to the shifters.
I think youll pretty much have to learn how to time it right. I have this slight hill when i get off the HWY and i hit a red light, So lets say i sit in the red light and go, if i got slow and accelerate and decide that i want to accelerate harder it will lag the whole operation untill i reached that little hill and suddenly decide to shoot. it will still drive but it wont accelerate more than snail speed... so heres what i do
my car has the shifters so i just start going like normal and a second or two later downshift to 2nd and it just feels like it should, suddenly your going the whole hill hard and it keeps going! i let it just drive that gear and it automatically goes back to D within 3 seconds.
With a DS car like my G i would just suggest to put the car in DS mode while your at the red light, accelerate normal. and then downshift to second and as soon as you feel like you dont want the sport mode just slap it to D.
Anyways goes hope this helps everybody good night