Slowbrick;52040 wroteI can see that the pre 90 has a more "square" style tube runner design. By design this will introduce a less smooth flow of the air passing to the turbine and therefore a little more restriction than the more tubular design of the 90+.
A square tube is less efficient than a round tube, but in this case the only thing that really matters is the width of the log manifold's square tubes vs the diameter of the 90+ manifold's round tubes. The head also has squared exhaust ports.
A shorter run from the head to the turbo should make for a more efficient system, other factors aside.