Streetmaster to Airgap

SM intake. What we are seeing is a history lesson from Edel....before they knew it was a history lesson.
If you compare the runners on an old school LD340 intake & a Perf intake, the Perf has smaller runners. Both were listed by Edel as 5500 rpm intakes. What you see here is a 20 yr technology gap where Edel learned [ slowly ] that bigger is not better because the Perf int has runners with a smaller CSA, & a trapezoidal shape in the runner bends.

This is what is being seen with the SM intake comparison. The small runners are not nearly as restrictive as they they were thought to be 'back in the day'. Hence the close HP #s.

I learned the hard way also. When I bought my 750 Honda m/cycle, I was given a spare cyl head with it. I immediately enlarged the ports because 'those small ports cannot possibly work'. The bike was slower everywhere with the bigger ports.