MT15 sprocket on R15 V3 to make it faster

I decided to install 52T MT15 rear sprocket on my 48T R15 V3 to make it faster.
I was unable to access the top end of my R15 V3 and hence I decided to make this mod to boost my bike's acceleration and top-end performance. I'm almost 90kgs heavy and I believe that is one of the main reasons my bike can't go as fast as I want it to, so I bought the original MT15 chain sprocket set and put it on my R15. I later took it on the highway and tried to test its performance. Although the pickup had noticeably increased, I was quite disappointed to see the top speed on each gear decrease. I wasn't able to test out its max speed, but I was quite pleased with its performance.