All the E36 325 in ITS/ITR are OBDI and ALL have the same manifold...

The M50NV (non-VANOS) is 1992 only
The M50TU is the VANOS model from 1993-1995
*The above reside on the same spec-line*

The M52 is the 2.8l OBDII from 1996-1999
The S50 is the OBDI '95 M3 3.0l
The S52 is the OBDII 96-99 M3 3.2l

The M52TU is the E46 2.5l (99-00 323)
The M52B28 is the E46/Z3 2.8l
The M54 is the E46/Z3 3.0l
ALL of these are OBDII and Double VANOS

FWIW...The gains are not 15-20hp when swapping on an OBDII car...those are Dinan/Conforti type numbers for sure...there is a gain of course...but to realize greater gains requires larger injectors and a larger HFM (MAF) neither of which woulkd be IT legal anyway.

This is the exact reason I said the '95 M3 should be allowed in ITR...1995 ONLY uses the same 17.5# injectors as the 325's and the same 3" MAF (as does the 96-99 M3 FWIW). With the 17.5# injectors and no MAF swap the power differences will be minimal... .5l greater capacity and slightly hotter cams.