I believe the '91 model had 6.5" speakers. The strange thing is, the designers DID put a lot of thought into the sound system - the speakers mount into sealed enclosures in each door, and different enclosures in the rear pillars. They fitted components front and rear as standard. Apparantly this was one of the best sounding stock installs of the time (I can't tell because the stock head unit is knackered).

It does seem odd to go to all that effort and then fit 4" speakers. Luckily the 4" Diamond M3's sounded incredible in the showroom so I'm crossing my fingers.

Rob