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here are last years trim readings with all the mods including the 996 tune ...
date FRA (load 0.7 to 1.32) RKAT (idle +/- 4%)
21-May-17 1.00, 1.01 1.92%, 1.35%
22-May-17 1.05, 1.06 1.96%, 1.64%
17-Jun-17 1.04, 1.05 1.78%, 1.40%
21-Jul-17 1.05, 1.07 2.48%, 1.82%
these are all after hard workouts at the track, so real long-term trims.
so, as you would expect, load trims are fine. While the 996 tune is designed for a bigger engine, it is still just a matter of look up airflow at the maf, and check a table to confirm appropriate amount of fuel for airflow - displacement doesn't matter. idle is different, so the ecu will have to trim it a bit more to work with the 3.2 but, as you can see, still within tolerance. my concern with the 996 tune was that the load triggers for the switch to open loop would be off - rpm, engine temp, throttle position - however all seems good and engine working like a top. in fact, seems to be better than before (no dyno or anything) which seems to indicate to me that porsche neutered the 986 with the tune as well. finally, since low load trims are so good, i am confident that the open loop fueling is fine (open loop is un monitored - our cars only have narrow-band o2 sensors so can't monitor high load operation when the dme is adding additional fuel for cooling purposes).
putting a 996 tune on a 986 is no big deal - anyone with a pst2 or piwis can do it in about 5 mins - the tools come preprogrammed with all the 9x6 tunes and variations (ROW, NA, various changes for various years, etc.). great chance to get a row tune at the same time (delete cats/sensors and smog pump with no cel). what you will need is your dme programming code - available from porsche if you can find a willing dealer to give it to you (mine cost me $50). after you have the 996 tune on, realise that your car will read as a 996 or a 986 depending on what system you want to look at with your pst2/piwis/durametric.
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