Q. What is a Euro M3?
A. The European specification M3 was introduced in 1993 and included several parts (S50 B30 & S50 B32 engine, lighting, rotor discs, powered rear windows (coupe), sequential transmission option, and more) which were deleted from or modified for the US M3 (introduced in 1995). The Euro M3, with an engine more adept to high speed (top end horsepower) than off-the-line acceleration (low end torque), is quite different from the less expensive US M3. For more information, visit Die Inoffizielle BMW M3.
Q. What is a lightweight M3?
A. Detailed information on the M3 Lightweight can be found at http://www.bmwworld.com/models/m3_ltw.htm. See below for a brief description from BMW NA (edited):
The 1995 M3 Lightweight (BMW NA model code 9520) was produced between 8/95 through 10/95. A small quantity (approx. 100 units) of M3 were produced, aimed at the performance purist and/or active competitor. This street-legal model (as delivered to the dealership) eliminated several comfort and convenience items for weight reduction purposes which were normally found on standard M3 models. The M3 lightweight came with several performance upgrades based on the European M3 GT homologation series for worldwide GT racing.
Q. What is a luxury model M3?
A. From 1995 through 1997, BMW offered a luxury package to compliment the M3 line. The model included 8-way electrically adjustable seats, extended leather on the door panels, chrome interior door handles, wood trim throughout the cabin, cruise control, on-board computer, M-Technic side sills, M-Technic front spoiler, and M-Contour wheels. The additions (mainly the seats) increased the weight of the M3 by about 125 lbs.
Q. Why do the 1995 and 1996-1999 M3s have different engines?
A. The 1995 M3 (engine code S50US B30) was equipped with a Bosch DME (M3.3.1) with OBD I, whereas the 1996-1999 M3s (engine code S50US B32) were equipped with a Siemens DME (MS41.2) with OBD II. Also see below for a dated, yet informative, response from Jim Conforti (edited):
There will be 1995 M3s until December. There will be no 1996 M3s since the S50US B30 engine would have to be emasculated to meet the 1996 emissions regulations. At that time it was presumed that there would be a 3.2L version of the new 328i 2.8L alloy L6 for the 1997 M3. The 1997 M3 was supposed to hit the shores in the summer of 1996. However, a slight glitch has hit. The 2.8L was to be made of Nikasil alloy, the same used in the M60 V8 blocks. This material was found incompatible with a lot of US fuels due to sulfur content, so for the M60 they are going to sleeve the blocks in the 3.x and 4.x liter V8s. There is not enough meat in the 2.8 block to sleeve, so they are changing the alloy to Alusil (same as the M70 V12) which is immune to sulfur but more expensive. This is requires reengineering the 2.8L and presumably 3.2L M3 blocks.