^^^What he said. There are a lot of factors missing here. Budget is the biggest. How low are you wanting to go? What are your goals?
A popular method of lowering here are the Swift springs. They are relatively cheap and close the wheel gap pretty good with the sport 19's. There are other springs that lower the car more but you would have to do some research here on the forums to get the amount of drop.
If you want adjustability you could always do coilovers. They are more expensive but most allow you to adjust the damping and height. You can get a set of BC coilovers for $1000. Thats the lowest I have personally seen. I havent really looked though. For tracking KW makes great quality coilovers. They are more expensive however.
Just do some research around the forums. There are a TON of threads asking this exact question and there are threads that offer more information than you would probably want to know about the subject lol.
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2009 370z touring w/sports package
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