Well, I finally made it back to the dyno, this time instead of just making about 3 pulls for a baseline, I made about 25 pulls, ha ha (I had some other testing to do in addition to the intake swap). Anyway, I tried to get some numbers down low, like 40% throttle and 2-4k rpm, but with the converter and the operator trying to hold 40% throttle immediately the results just weren't consistent(they don't let you drive on the actual dyno, which drives me nuts, but I was sitting in the passenger seat and he did a pretty good job regardless). However, I did get pretty consistent results with the WOT pulls so that is what I will show. Here is the chart for single plane vs dual plane with the FAST EZ-EFI throttle body on my engine (you'll notice the graph is not smooth at upper RPM, thats because the swampers don't like approaching 100 MPH (118 was the fastest reading). Both of these pulls were with the 36" TSL tires, the next post will cover what happens if you simply swap tires...
You can see the new setup made about 12 more HP peak and 17 more lb-ft of torque peak. And midrange was stronger too, from 3600-4100 it was 20 lb/ft higher, sometimes only 15. However, below about 3300 the graphs cross. At 3000 the dual plane had 4 more HP and 6 more lb-ft. I could not get reliable data below that, and to be honest, I think the lower the RPM the less consistent it was, trying to measure the power through the 10" stall converter was probably too dependent on fluid temp and such at lower RPMs. At upper RPMs there was low slip and it didn't matter. If it was my 4L80E I could of locked the converter to see. My point is, the lower the RPM, the less reliable the numbers are, and the higher the RPM, the more reliable.
So to me the data make sense. The dual plane might still be making very slightly more power at low RPM because of the longer runners. However, the single plane clearly outperforms it at upper RPM, even with the throttle body EFI. I will say though, that it is smoother to drive, and has better fuel distribution with the single plane and this EFI system, and it idles smoother, and runs better at part throttle. The dual plane is supposed to supply a better signal to the carb at low RPM and throttle, this is not an issue with EFI.
The way it runs at low RPM is better and it has less hesitation and runs smoother with the single plane, this alone outweighs the missing 4 HP at 3K RPM(and I can likely say that 4HP is less than the margin of error at that RPM through that converter on a wheel dyno). When you add on the power and torque gains at mid and high range, I would definitely recommend the single plane for the throttle body EFI if you are purchasing an intake manifold. If you already have a dual plane and are swapping on the EFI. Then I say just try it and see what you think. If you are getting hesitations at low RPM and your plugs show uneven distribution, then you will probably like the single plane better. If however, your plugs look even and its running smooth at all RPM and throttle positions, then keep the dual plane. That was not the case for me, even though I ran the dual plane with the EFI for 7 years and about 6K miles with very few issues.
