From your other message as well:
"Two Porsche dealers, and the shown TSB 1001, seem to say if you change the oil cooler to one of those new tiny ones, that you have to change all of this other stuff, add adapters etc. It is a mess. The simplest thing is to just replace the original part and drive away. There definitely is some connection between the oil pump in the front, the oil cooler on top , and the changes that would have to be made to the expansion tank in the boot. Changing the cooler will affect the velocities, the passage lengths, and the volumes.
In any case, there must be some reason why Porsche says to change all of these parts if you want to use a different part than they originally designed for the application. I don't know what the reason is, and neither does anyone else that I talked to. But they all agreed that it must be done. I lost a lot of time, and a bit of money putting deposits down, and waiting for parts that I will not use, trying to follow well meaning advice, on how to Hot Rod the Boxster, instead of keeping it stock.
This is relevant to the oil cooler thread because Porsche says all of these thing must be replaced when the oil cooler is changed on the original Boxster."
OK, let's take this in steps: I have absolutely no idea why the oil pump has to be modified, if that is in fact correct. To my knowledge, the very old style oil cooler, the one without a top coolant bleed and that requires the adaptor plate to mate to the engine, is no longer available. As such, the newer design is the only available choice I can find in the Porsche parts system.
As for the coolant tank, that has previously been discussed in this tread; the early tanks did not have a connection for the small coolant vent line on the top of the cooler to connect to, this was a design error that Porsche corrected. The small line lets air trapped in the coolant section of the oil cooler vent to the surge tank; the first cars did not have this line and Porsche discovered that air collected in the oil cooler and caused problems, so they modified all cars going forward to have the line from the top of the oil cooler to the tank. Early cars that still have their original coolant tanks (and there cannot be very many) can still use the newer cooler with the nipple by simply plugging the outlet with a small section of blocked hose. As most of the early cars have long since changed out their surge tanks (they were prone to cracking), they probably already have a tank with the connection for the line (albeit plugged for the same reasons); if they do, it is a simple matter of running the rubber hose from the cooler to the tank. Either way, the new cooler works.
As for the oil pump section modification, I know the 97 cars had a different oil pump than the later cars from the part numbers in the PET, but I have no information on how it is different. Physically, the unit looks exactly the same as the latter part numbers, so what ever changed is not readily visible. The 01 and 02 cars also have different oil pump part numbers, but without explanation as to why. Porsche often changes part numbers as they update components due to information accumulated with owner miles, so that is nothing unusual. It is also not unusual for Porsche to want to sell you the updated components, particularly if the one you have are known problems, which appears to be the case in the TSB 1001 you quoted.
But what I have confirmed is that if you read the entire TSB, you will note that it clearly states that it is addressing oil/coolant intermix problems on the 97 cars. If further goes on to state that even if the oil cooler on the car is found not to be the cause of the intermix issue, you should change out all the other parts while you are in there as well. So the other parts are not actually required to change out the cooler, but are precautions against a future intermix issues from the other components.
What I can tell you is that, as mentioned earlier, we have quite a few cars running the newer and larger cooler, including a couple early models, none of which had the oil pump changed or modified, and all of which continue to do fine everyday to my knowledge. So I fail to see any validity in the comments about "velocity" or "passage lengths"; and as the oil cooler had nothing to do with the intake system, the "breathing" comment is equally questionable.
I am sorry you seem to have run into so many brick walls on this simple and very common upgrade, but as mentioned, with so many done and having run a lot of cumulative miles, I know it works.