I think they would be a great upgrade, but if your running the factory carb turbo system its almost a moot point.
a decent set of p/p 8445's will probably make comparable horsepower just because of the restriction that the factory carb turbo intake itself is. Just need more intake/exhaust flow to get the most of those heads. And its kinda hard to improve enough to make them worth the money in my opinion.
not that I know of, theres been rumors of slurry porting intakes, but I have no official data on the results.
any improvement to the stock lower intake will make more power, to the point to where some of us have swapped the intake out in favor of a better design. this however makes the whole deal a custom setup.