p1520 is definitely the camshaft sensor code. exhaust camshaft i believe. fairly common. probably causing the vanos to not work right or at all. id replace the sensor. awesome diagrams can be found at bmwfans.info, and id get the part from the dealership or pelicanparts.com.

brake lights not related to that code or issue.

edit- so i reread and maybe i misunderstood about the brakes. i thought you meant the actual lights on the back of the car coming on and off. if you mean the "brake lights" warning light, its from a bad connection in one of the lights. its thinking theres no bulb/blown bulb when really its fine.

good luck dude! also, you should swap over an m50 intake manifold from an obd1 e36 325i. its runners are twice as large and youll get some good power from that. i can probably hook you up with one and explain if youre interested!