In north America:
E30 M3 (quite possibly the best sports
car ever made)
- 2.3L 192 hp Inline 4 S14B23
1995 - 3.0L 240 hp Inline 6 S50B30
1996+- 3.2L 240 hp Inline 6 S52B32 (the 3.2L saw an eleven ft/lbs increase.)
"Best-Handling Car Ever – at any Price" - Car and Driver (`97)
- 3.2L 333 hp Inline 6 S54B32
- 4.0L 414 hp V8 S65B40
No factory M3 to this date has been powered by a V6 engine. If you do not know the difference between an inline and a "V" configuration, I suggest you educate yourself a little more before writing a definition.
All M3 (to current date) came stock with naturally aspirated engines. This means they do not need the boost of Forced Induction (see: Mercedes) to make massive power from small displacement.
Despite the RS4 having a larger engine, producing more power, the E46 M3 is quicker around the track.
E92 M3 beat C63 AMG and RS4 around the track.