Click on the Hyper Mods button to your left to see what can be done to make that thing hum. Most people start out doing everything except the grate first which makes a world of difference.
26psi - Humm! I would think you are referring to the boost provided by a turbo charger. I know swat about gleaner rotary combines but do know a little about turboed engines. That sucker better have an air to air intercooler on it.
Your dealer might have some information on it. The factory did update early models and there may have been a new serial number issued to these models. Otherwise, look at the tag closely to see if it has been altered. And secondly, make sure it is a combine serial number tag.
The tag you are looking for should have several letters followed by numbers and above the left rear wheel. The last 4 numbers are the serial number. My N6 has a GH in the serial number meaning Golden Harvest edition, it is an 82 with serial n5149. Either 83 or 84 has a Sixth_Silver Edition and had the S in the serial number. PETE has the proper year breaks. All 82's that I have seen are marked with "Series 3" on the side. Updates were put into many earlier machines but I never heard of a serial number change because of the updates.
Wow I sure forgot where the sn was. Darn stupid. I remember that plate now from the one we have. The machine has a natural flow sticker on the grain tank and has a tan cab interior.....the cab plate said N6 204. Should have taken my operator manual.