I would just clean the castings up my self. Ice and TT racing isnt about making the most HP. It is about having a smooth power delivery so you dont blow the tires off. It is traction that is the problem, not a lack of HP, especially if you already have a several.
If your wanting a true TT engine I would have probably went with a 4mill Passion 12 port TT engine. Probably not as much top end HP as a several but it would have the best power delivery.