I'm enjoying following this thread. As some additional annecodatal info, my shop generally advises against the IPD Plenum and larger throttle bodies on the M96/M97 Porsches. They have a dyno and have tested lots of cars before and after swapping plenums and throttle bodies. They say they haven't seen increases in power from the larger throttle bodies and plenums, and in some cases, have actually seen decreases in power. They advised me against adding the IPD plenum and larger throttle body, both when my Boxster S was a stock 3.2, and again when they rebuilt it as a 3.6 with a custom tune.
They use a Dynapack dyno, which doesn't have rollers, the wheels are taken off and the dyno is bolted directly to the driven wheel hubs. My 3.6 produced 254.7 HP at the hubs on that. I think I could get more HP with a more open exhaust, i.e. catless headers and losing the stock muffler, but I'm happy where I am, and the dyno time costs money!
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