We just did a QC with a custom cam dyno tune session. The last pull we removed the JMB air intake and ran open throttle body (single blade billet TB) to see if it was any restriction anywhere in the curve. The truck made the same or less power (within 3-4whp) the entire curve, no where did it make more power without the air intake. I have performed this test on a heads/cam truck, and a stock internals truck as well in the past and it has produced the same results.
During that session we would wait about 15 minutes between each pull to get accurate results. The coolant temperature and cool down process was the same for each pull to make it completely fair.
I have never compared it to a stock airbox, but I would find it difficult to believe a corrugated tube with a much smaller filter could make the same power as a smooth shorter tube with a huge filter. One thing is for sure, a JMB intake is not a restriction for 99%+ of NA guys.
