I'd assume it would be the same as upgrading the stock to larger TB in terms of gains. Your stock injectors are up to the task with your tune. Your CAI isn't an overwhelming amount of air like a supercharger would be.
I can't answer the tune question, but performance wise, they would do absolutely nothing.
Your car's computer is striving for an air/fuel ratio (using the Mass Air Flow (MAF) Sensor and the Oxygen sensors)...if the stock injectors can make that ratio - you are all set. Oversize injectors would just work less to give the same air / fuel ratios but performance would be the same.
Oversize injectors can actually hurt performance. The shorter duty cycle and larger flow ports can lead to less efficient fuel distribution in the cylinder.
What Klaw said. There's a grey area, around 380-400 rwhp, where you could use either the stock (29 lbs I believe) or upgrade to 39 lbs injectors. But bellow that bigger injectors will not help and could hurt.
Dan