I run a STR 14 - 6 which is similar but different and had the same thought. A friend suggested I make a plenum spacer, so I did. I made it out of 1/2" 6 ply poplar plywood. The car liked it so I made a second one, stacked them, and ran it. It didn't like the second one. I suspect because there wasn't "enough motor" under the intake. I figure the spacer was worth a tenth. I think the plenum spacer works because the lid in the original configuration doesn't have enough roof over the runners. The air has to make a real sharp turn to go down them and carb spacers makes 2 sharp turns. Just my This is w/ 2 spacers,not 1 which I still run.