Gary,
We are not talking about the first gen Venture. We are talking about the first gen Royal Star. As to why they made so much less HP, it was because Yamaha was trying to design a bike that looked like a cruiser. In my opinion, they succeeded in that and it's a great looking bike. In doing so though, they went with a small air intake/filter and then due to the reduced air flow also used smaller carbs. Baron's offered what they called a "Big Air Kit" that solved the restricted air issue and then with the proper re-jetting, got the HP up a good bit. To really get the HP up though, some people have built special manifolds and installed larger carbs after increasing the air intake size.
Also, they did not have the same size carbs. The early Royal Stars had 28mm and the later ones have 32mm. That is why some people change them after increasing the air flow.