Ok, I am going to show you how I modified the ahu/1z front intermediate shaft bearing so that it shouldn't be as failure prone. Although I did get a bit carried away while doing the repairs and forgot to take pictures as it was going back together.
These next two diagrams show the Timing Belt routing for the 1.8 gasser and the ahu/1z (which bassically share the same block) and the fact that the timing belt runs on opposite sides of the intermediate shaft pulley. This rearrangement of the timing belt is the majority of the reason that this front bearing is prone to failure, it not only changes the direction that the shaft is loaded but also the direction that it turns. The thrust load of the timing belt can also be exaggerated by adding a larger injector pump head (like 11 or 12 mm) because the force required to turn the pump increases and the tension on the timing belt also increases and therefore the thrust applied to the I-shaft bearing also increases. The oil hole in this bearing was positioned in the correct place for the gasser engine(about 10 o'clock) but completely incorrectly for the TD/TDI engines.
These next two pictures are taken from above the motor looking down at the wear on the thrust side of the TDI bearing. You can see a difference in color/shine at the wear/no wear interface.
This picture is looking up from the bottom of the motor at the oil galley hole that supplies oil to the bearing. It is quite literally 180 degrees opposite of the thrust load on the tdi I-shaft, this means that not only is the T-belt thrust pushing the shaft toward the dry side of the bearing but the oil pressure coming out of the galley is also adding to that thrust force.
Here is the practice groove cut into the back side of the bad bearing that I removed and then the two new bearings with the grove cut into the front bearing. The bearing shell is only about .060" thick and since the babbitt material on the inside of the bearing is .005" or so thick the groove should only be cut .035-.040" deep and the width of the oil hole in the bearing.
This looks out of focus but it is so you can see the groove depth at the side of the bearing.
New bearings.
This is where I quit taking pictures because I was so excited to get it all back together. But it goes together just like the original except that the front bearing oil hole gets clocked down between the 4:00-5:00 mark so that the oil enters at the beginning of the thrust area and is swept under the thrust area as any plane bearing is typically installed.
Now the repair I have done here is for an engine that is not completely disassembled. If you have an engine block that you are rebuilding and is just a bare block I would perform this repair differently, I would machine this grove into the bearing bore in the block itself (1/8" deep and the same width as the oil galley hole) then using a standard bearing (without any modification) the oil hole in the bearing would be located down at the 4:00-5:00 mark.
If you have any questions feel free to ask I will answer them as best I can.
Thanx for looking,
Jaysin