what are you using the sled for, dragging or trail riding/lake running?
also seeing as how you are going from 7800 RPM to 8400 RPM, your gearing will also need to be a little different. you are geared for about 10 mph higher than you were when you were pulling 7800, that may be the reason your clutchs are not shifting the same try going one tooth bigger on top, the extra power you supposedly got from the pipes and such should be able to pull that, or it might even pull the gears you have now, once you get it set-up right.. Do you have acess to a gram scale? you can take a little bit of weight off those pins(2 grams or so) and that may help a little.
also you have a purple pink spring in there, you should try a green/white(200/380) spring, it will bump up your engagement a few hundred RPM and your top rpm will come up a 2 hundred or so. if you change the spring, do not do anything to the pins until after you change it, then you may just have to take a very small amount off of them.
as for the secondary, i have had good luck with a 50/47, with a white spring @19 pounds
hope that helps, anything else just post