What' the story on the upper pipe, is it just larger than the one that comes with the kit? I doubt it will make a huge difference unless you are looking for more than a few hundred horsepower. Don't get me wrong the kit will run right out of the box, it just runs rich as hell that's all. I run RC injectors, I haven't had any problems with them, just make sure you order the harnesses too, they don't come with the injectors (learned the hard way on that one :x ) I spent about 2-3 hours on the dyno not including setup (o2 sensor, etc.), I'm guessing about 6 pulls.