Isn't there a theory that was never really proved? SU's gave you slightly more power but worse economy. Strombergs the other way around. Hence why they never put Strombergs on Spitfires. Although, didn't some US spec Spitfires have Strombergs? A very very small number. Or is that just an old wives tale? When I put twin SU's on my engine I did notice an improvement in torque. But then, I only put them on because the Stromberg was knackered so can't really comment.