Is there some reason why you want to keep the 30 pound stock exhaust monstrosity? By lightening the Busa with a 9 or 10 pound 4 into 1 performance exhaust system and adding a Power Commander you could easily gain the equivalent of 10 to 12 horsepower.
Your gains from the Yosh cams will be greater with a higher flowing exhaust system as well. In general, a 4 into 1 exhaust system flows better at higher RPM and that's where the biggest advantage from the cams are found so you're matching performance parts with other performance parts which work together for a greater performance yield.
Also, since the Yosh cams are mild cams anyway, it's really a must to have them degreed to yield max HP from them. If the cams were able to yield 50 to 60 HP just by dropping them in, who'd give a crap about losing a few HP by not degreeing them but these Yosh cams yield more in the order of 6 to 8 HP on an engine that's already running with proficiently degreed stock cams so, you can't afford to waste any HP by not having them degreed.
Another thing to consider...If you are going to install cams, you'll need a fuel curve remapping device like a Power Commander to remap the already lean and rich areas found in the stock mapping. Cams allow for more air flow. With more air flow there must also be more fuel added.
My recommendation: Go for a performance exhaust system and Power Commander first. This way, you've got your HP increase and lighter Busa while still retaining stock dependability and don't void the warranty. Should you decide you still want more power, by all means go for the cams. This way, all other performance parts are already in place to make and feel the best increase from the cams.
True performance is never cheap...
