I've owned my G35 coupe for about 4 months now it has a little over 100,000 miles on the car, recently I noticed a grinding noise when starting the car and when I first give it gas it grinds as well and along with that a noticeable throttle lag, anyone have any ideas what this could be?!!

 

That is likely a timing issue, could have a broken slack guide or chain guide.

 

That's what I was thinking as well, what kind of money would that cost, I would assume a whole new timing chain would be needed

 

If you have an 06 or below you can take off the black covers to see how much slack there is and if the plunger is all the way extended.

I did a primary chain replacement myself on my car and it was about 500 bucks in parts (water pump, chain, guides, o-rings, guide rails, etc..)

Nissan quoted me about 1200 bucks in labor to do it alone, since they were going off AllData.