We all genrate more questions than answers, that's what makes these forums so good, just need to try and keep the thread 'on-topic', that's the hard bit.
For a potted history on the Rxx series, best look at the history page on the SDU site, it will give lots more detail than I can ever put in here.
Then of course there is the differences between the engine types, The RB26DETT is fitted to the GTR's and has many differences from the RB25DET fitted to the GTS & GTT not to mention differences across the Rxx series also.
RBxxXXXX deciphers like the following
R - Race
B - Bred
xx - engine CC
D - Double over head cam
E - Electronic fuel injection
T - Twin
T - Turbo
The RB26 comes with individual throttle bodies per cylinder, two turbos, a large front mount intercooler and some other bits'n'bobs.
The RB25 comes with single throttle body, one turbo, a small offset intercooler, and a less bits'n'bobs.
The RB25 fitted in the R34 makes about 30bhp more than the one fitted to the R33, and power is reduced by about 10bhp in the auto versions.
Generally speaking the auto transmissions used are found to be very adequate within the scope of the power they were designed to handle, So if you tune it like mad, you'll need a new box. A manual conversion will be very involved, what with the auto's integration with the engine management software.
There, that little lot should keep you going for a bit
