I'm told by my tuner that a high flow filter can push a lean map too lean. Whether or not it can cause a melted piston or not, who knows? Personally, I don't get going to a race filter with a stock header. You're not going to get much benefit from the filter with the pipe plugging the air moving through the engine. A stock bike can benefit from a Dyno to, mine certainly did. However the most improvement was down low in the rpms where the stupid lean OEM tune was causing flat spots and I actually lost some hp on top.
I started with Yoshimura R77's slip ons on my 09. I rode it like that for 6 months without a tune or anything and all was fine. If I was doing it all over again, I would have gone to the full exhaust from the start. Mainly because of these factors:
1. Since there are 2 cans on the stock bike, the slip ons cost almost as much as a full system. In the case of Yoshi, it's the exact same can, just one of them on the full system. The Yoshi full system in SS was actually $50 less than the R77 slipons! BTW most won't sell the full system without the cans. But keep your eyes open and a used full system will pop up. An exhaust is just tubes, if it looks ok it probably is.
2. The full system sounds 1000% better than the slip ons. At full tilt, you will wet your pants!
3. The engine feels opened up and revs better with the full system. Very big difference.
4. With a full exhaust, race filter, and tune you can get 10 hp or more. With the slip ons probably nothing at all performance wise.
5. Many prefer the balanced look of the dual cans. I like the easy access to the chain for cleaning and lube you get with the single can.
6. One can is lighter, so the weight loss is even more over OEM.
I think you were getting good advice in this thread. I stuck my big mouth in here to make it clear if you are adding slip ons stop with that. No filter. Tune it if you want but this mod is only about looks and requires nothing more than putting on the new cans. If you want to go to the next step (full exhaust and filter) you have to tune it.