A lot of people neglect to mention their top speeds are measured going downhill! Even an ever so slight downhill grade will significantly increase your top speed.
I messed around for months with a clone, then a Genuine Comet driver on my Baja, using various combinations of springs and never could get it to perform the way I wanted. It would upshift too fast and bog the motor even with a yellow driven spring in the tightest hole then refuse to down shift when I slowed down, despite the fancy moly lube. Got a Juggernaut Super 30 driver and it felt like I was driving something off of the Honda production line, revs to the moon now. I run it hard and it is still cool enough to put my hand on, vs the Comet which would blister. Really shows how much power it was wasting.
All said and done it'll probably hit 40 or so on relatively flat ground in the 200 yard straight stretch we have in the riding area and I weigh around 225.
Put one on my oldest son's Trailmaster a few months back, runs great even with the throttle limited to keep the speed down. Just ordered a third for my youngest son's Coleman.
Because of the lower final drive ratio vs the Comet, I can see where some get a lower top speed, but, to me, the increased off road performance is worth it.