the bigger question is will the tire that fits on that wheel fit into the wheel well without rubbing. we know that they are NOT going to fit into the front wheel wells as they will rub on the fender lips and the front struts. on the e9,
@vince runs a 9" x 17" wheel on the rear, but there is very little clearance. you will probably have to roll the rear fender lips to fit.
the rule of thumb is 7 x 16 fronts (et 11) and 8 x 16 rears (et 24). et 38 is going to be very difficult as its going to push the wheel further. there are ways to increase width, but they are not inexpensive. the first is coilovers to reduce the spring diameter ... the 2nd is fender flares. so what this means is that inexpensive wheels will be very expensive to fit. better off to spend a bit more money and get wheels that will fit. there are aftermarket Alpina style wheels from various sources that will fit with camber plates and rolled fender lips. i would recommend looking into the Coupeking Alpinas - look just like the real Alpinas and are well made ... and half the price of real ones. there are also wheels made by maxilite (i think) sold by places such as Ireland Engineering or other online sources