Now just imagine the power the two-strokes would have if they were designed to be that loud. I do think that if the engineers set out to make the most powerful two-stroke possible, noise be damned, it'd open, loose, and loud as hell. Of course, matching the 4T sound level is the wrong way to go about anything, but if it were acceptable to go up to 130dB or so, I think we'd have some pretty radical power in our court.
While I'm no engineer, I don't think this is true... as discussed before a properly tuned modern two stroke needs back pressure to produce power... while it might be true that you could get a few additional horsepower if noise were not an issue is possible, I just don't see how.
As for getting more power, if all you want is horsepower... the kart guys are getting 70 to 75 horsepower out of a 250cc engine!! This would not be usable in an mx bike for two reasons, first and most importantly, it would break the rear wheel loose at inopportune times, and basically be unridable. Talk about a light switch!
Second reason is the pipe design parameters on a bike... by it's nature there must be twists and turns i to fit it on the frame and not have it stick out too far on either side. Plus the diameter needs to be larger in order to produce such large horsepower numbers....
Now maybe if you flipped the engine around on a two-stroke...... with the exhaust coming out the back.... hmmm...
Check out the exhaust coming out the rear of this old Honda.... if this was built in the 1950's how come Yamaha calls it advanced on the 2010 YZF450 tank??