Looking in default files under the BMW E93 335i section, it looks like someone made a copy/paste mistake or something for the following:
<frame canid="0x1b4">
<value targetId="170" offset="0" length="4" conversion="(((B1*256+B0)/160)+((B3*256+B2)/160))*0.5*0.01"></value> <!-- fuel level -->
</frame>
It should be…
<frame canId="0x349">
<value targetId="170" offset="0" length="4" conversion="((((B1*256+B0)/160)+((B3*256+B2)/160))/53.0)*100.0"></value> <!-- fuel level -->
</frame>
The case of the canId= is wrong (the ‘i’ needs to be uppercase) and the can id itself is wrong. The formula didn’t make a lot of sense to me either. The above worked fine for me. You have to change the 53 to the # of liters your car has. I have a 128i so the total of both tanks divided by 53, then multiply by 100, gives you the % full.