We use the sporty needle unmodified slide and stock springs with stock pilot and main. Turn the idle mixture screw out two turns to start, then re-adjust after the engine is warm.
2500 RPM's is where the carb transitions so the sporty needle should take care of that. Shimming the needle up does not do the same thing and we find it does not make the mixture as good as the sporty needle. The above will give you dyno readings within a few horsepower or so of some of the best dyno tunes we've seen for a lot less money. Hope this helps.