I recently bought a obd 1 code reader and I went ahead and scanned my 90 gt. I did a key on engine off test and I got 11 of course but I also got code 10 and 20. I can't find them in the list of codes but I can find them in the book under the codes for a cylinder power balance test which is weird because I did not do a cylinder power balance test. Could these be stored codes or maybe I didn't follow the procedure correctly?