I have a '97 standard and had also the popping.
Now I finally got rid of it and I think there were 2 causes :
1) my left exhaustbolts did I tighten I don't know how many times, but each time after a ride I checked the left bolts and could tighten them more till the 7th or 8th time that it was finally O.K.
I did it with a torque-meter. So if you install new gaskets for exhaust, please check and tighten each time till they are finally good!!
2) did the carb synchronisation many times now, better cannot - I cannot, but they are very close when machine hot - this can also play to get rid of poppop I think.
This is my experience, I am glad without the pop
