I'd recommend the bigger ones, 660. Leaves room to grow. Been down the road of injector upgrading and wouldn't repeat it without a really good reason.
"A car just isn't a car without a little blood, sweat, and beers." -- Shadowfire
I understand both reasons to keep the 660 and keep the 310 u both make sense and good points. My big problem now is I can't find anyone to tune this thing. I live in Orlando FL.