^^^The last two lines you wrote are excellent points!
Here is something that I forgot to copy and paste from this Audi Wiki page concerning the aforementioned transmission(s). I'm sorry to dwell on this, but it's just that I really want to know what our transmissions are capable of, and which variation our TDI's do have. The ZF 5HP-19FLA was already mentioned up above, but there seems to be one other one without the letter A in the end. The one without the letter A is a weaker one as far as potential maximum power capabilities are concerned. Here is the copy and paste of the info.
B5 A4/S4 (ZF 5HP19FL and ZF 5HP19FLA)
There are two different automatic transmissions in the B5 A4s. In 1998, Audi introduced the Tiptronic feature. There was no change to the transmission, only the control module and shifter. If your A4 is Frontrak (front wheel drive) you have the ZF 5HP19FL tranny. If your A4 is quattro or you have an S4 you have the ZF 5HP19FLA. The 5HP19FLA in the quattro cars is designed to handle more torque than the 5HP19FL in the Frontrak cars.
Max Torque Specs:
5HP19FL = A4 (1.8, 2.8), A6 (2.8), A8 (3.7) Input Torque = 310 Nm (~ 228 Ft/Lb)
5HP19FLA = A4 (quattro 1.8, 2.8), S4 (quattro 2.7), A6 (quattro 2.7, 2.8, 3.0 ), Allroad (quattro 2.7), VW Passat W8 4motion, Input Torque = 420 Nm (~310 Ft/Lb)
Many people have said that the B5 A4 auto tranny is weak. Some people say the transmission is a lot stronger than most people say. Let me put forth some reasoning on the subject.
Some people that believe the A4 auto tranny is weak don't realize there are two different versions. Looking at the torque specs listed above, it is obvious that the Frontrak transmission is weaker than the quattro transmission.
The A4 quattro 5HP19FLA transmission is also used in the B5 S4 cars. They are frequently chipped to 382lb-ft torque (APR chip) and run just fine for years. One person (Cole on Audizine) claims 431lb-ft of torque to the wheels on his S4 with an upgraded torque converter. The only known differences between stock B4 A4 quattro and B5 S4 transmissions are the gear ratio and the torque converter.
A lot of people don't think about upgrading transmission components on the automatic transmissions when they start putting a lot of torque down. With a manual transmission, wouldn't you expect the clutch to start slipping and need an upgrade when you start putting down some real power? The same goes for the automatic transmission. When you upgrade the torque converter and valve body in the transmission it can handle a lot more power safely.
The rest of the article can be found here.
http://www.audiwiki.net/Automatic_Transmission
So with all that Oilhammer, I wanted to assume 100%, that our B5.5 Passat TDI has the "FLA" one and NOT the "FL" tranny. If so, then this will make me feel MUCH BETTER that my car is not equipped with the more durable stick, and I MIGHT just as well take the tuning on the car a smidgen further than the RC2 and upgrade the turbo when this one(if ever) decides to bite the dust.