Do you think that the bike has actually lost power or has your skill increased and now the power isn't enough?
If you are looking for a new bike because the bike you already have needs maintenance then I think you are going about this all wrong.
If you are looking to race, the first step would be to establish what class you would like to race and buy a bike that would be competitive in that class. You probably don't want to race in a 250+ open class. Go to the track, check out the races, see what class you would feel comfortable in and buy a bike that fits that class.
If you want more specific help then you need to fill out the "sticky" form located at the top of this forum.
Rod