Exactly the problem mentioned with my 2012 G37 convertible. It would feel like it resisted the acceleration or flat out did not respond. I could punch it to the floor and count to 3 seconds before getting a response. Other times I punched it and it acted like a teenager being told to do the dishes. Oddly enough, this struggle to accelerate was not all the time but under 50% of the time. I started to keep a log and noticed that it happened mainly in warm weather. When it was cool out, the car tended to react and perform remarkably better and not have the issue. In fact, the colder it got, the less it happened until I noted that it does not happen at all during the winter (yea great, just when I want plenty of acceleration on cold tires and cold road so I can slip...)
Then my back axle started making this ticking / clicking noise when torque was changed on the axle (forward to reverse or revers to forward or just acceleration and deceleration). The factory defect outlined in the Service Bulletin "2009-2013; Clicking Noise From Front Or Rear Axle During Take-Off/acceleration
When I got the rear axle fixed, it required disconnecting and reconnecting the electronics from the axle that presumably detects slip. Note that the slip detection has direct impact on the engine applying power to the rear wheels, decreasing the power when the wheels are determined to be slipping on the road. This also happens to be exactly how it felt when I accelerated... as if the slip detection was gently and evenly kicking in with the pedal being pushed down... Now remember back, cool weather to cold weather changed the symptom... and the nylon on the molex connector headers and wire housing for the electrical connections shrink and expand significantly (more than metal) in cold and hot. A shrinking wire connector would put more pressure on the connection making the electrical resistance lower if any corrosion existed between the contacts. Hmm....
So I get my car back from being repaired for clicking... and get in it ... and every single time I accelerate, it takes off like a bat out of hell. I don't even have to put it in Direct Shift (DS or Sport) mode. I tap the gas and regardless of my speed, it leaps. It was like I got a new car... or even more appropriately, it felt like my old G37 Sport Coup 6 Speed which hauled (*). (sorry, just no better way to express)
And like another poster, I was inclined to sell my car as I was so disappointed... but I love the looks, handling and the hard top convertible. Had I not had the factory defect (mentioned above) fixed and the acceleration problem resolved this would have been my last Infiniti.
So, long story short, if this happens again with my G37 I will be putting it on a lift and disconnecting, greasing contacts, and reconnecting every freekin molex connector anywhere near the rear axle. My favorites are Permatex (cheap)
or MG Chem Silver Conductive Grease