Which cats have you removed as there are three? It's better IMO to remove the pre-cats, and leave the main cat - or fit a decat and put it back on for MoT. You're wasting your time with the Bluefin, indeed any remap on the car is only going to account for very minimal gains.

As has been said it's difficult to extract more out of the 2.5 and you can find yourself spending hundreds to gain one or two bhp. A better bet would be to fit the 3.0 bottom end, or the complete ST220 engine.