60mm throttle body is a bit of a waste of time unless you've got cams, the engine doesn't flow enough air to get enough benefit from it without them, Mountune only found it marginally beneficial to fit the 60mm throttle with the MR200 kit and that had cams, full exhaust and the cast inlet manifold and it was only with all of that that the stock throttle body became a slight restriction.
An exhaust manifold and a map to suit will be your best option for power in addition to what you have already, then cams, then an inlet manifold, only if you're going that far would I think about changing to a 60mm throttle body.
An exhaust manifold and a map to suit will be your best option for power in addition to what you have already, then cams, then an inlet manifold, only if you're going that far would I think about changing to a 60mm throttle body.