My opinion? Aftermarket filters might be just fine but what if they are not? Oil filters are too important for me to risk using anything that might be questionable. I stick with OEM and same goes for aftermarket air filters. I own a BMC race filter but if/when I use it, it will not be longterm. The performance enhancement of race filters, oil and air, is very small. Stick to OEM and change as needed or according to the maintenance schedule.
Oil you can try different kinds. I use Rotella T6 in both my bikes and it seems to be no better than dino oil but it is cheaper and I have had no ill effects. I change it every 2500 miles just like I would conventional. Synthetic oil leaks easier than conventional. The crud left behind by convenyional oil might be keeping seams in the engine sealed and when you go to synthetic, it will get washed away and leak. This did happen on my Gen1 ZX-14 which is notorious for valve cover leaks. My busa doesn't consume any oil and 0 leaks so you are probably just fine to use synthetic. If you are willing to pay more, you might find a great one. I used Repsol Race 4T and it was amazing for 500 miles and then it was like normal oil. $80---I'll just change cheap oil more frequently but I swear that race oil was the smoothest that bike ever shifted, albeit short lived.
