Its been a long few months
:
The 3sgte has 440cc injectors which is good for about 240hp at 80% duty cycle. The reason I would tell you to go with 550cc out of a 7mgte (I think sard makes 530cc) is it gives you a little leway to expand in the future if you so decide too.
Lots of debate about that with the intercooler question........
The actual core has been debated whether its better or not, I personally don't know. I do know that a new intercooler core will flow better than a used one since its clean. And, to be honest, it looks a lot nicer too (bling factor). The piping itself flows more as they are generally bigger.
I think you should reconsider the factory Air Box with an SC setup. If you like the airbox design, think about getting an ARC out off Yahoo Auctions Japan ($$$$).