Check the foot peg bolts and mating surfaces - often need to be flatted and high tensile bolts fitted.
I have a simple but unpopular fix for the bad footpeg plate/bolt design - just change the bolts regularly.
The design is bad in that the bolts have to withstand quite a bad bending moment because the peg plates dont have a nice wide flat surface to mate with, where the surface could absorb the bending moment and thus reduce the bending moment on the bolt. As you ride you are basically constantly hammering on a lever arm with your whole body weight. Its almost like working the bolt back and forth with continual impacts on a long lever. The bolts have to withstand that on their own without any support from the frame.
No bolt, no matter how strong, is going to last in that environment IMO, without a crack developing and steadily growing. Its a classic fatigue problem.
If you know anything about fatigue, its all about the number of cycles to failure. The crack will develop at a steady rate, governed by the number of stress cycles it undergoes. The bolt will eventually fail when the crack eats into the bolt to the point that the remaining surface area is insufficient to withstand the stress of the next cycle. This takes a reasonably long time.
So all you need to do is routinely replace the bolts before then!
So I just put in new 8.8 bolts every six months or so. Its cheap and easy, and effective.
Most people dont seem to like this idea though, so you see quite elaborate fixes proposed on some of the forums. But without redesigning the frame to provide a wider flat mating surface between the peg plate and the frame its not really possible IMO, and there simply isnt enough space down there as far as I can see.