My 93 240 (automatic, 95K miles) is showing fault codes 113, 221 and 231 (according to my bentley book, fault in fuel injectors and rich or lean air/fuel mixture at cruise). It also stalls occasionally, usually when coming to a stop when its cold out, doesnt idle well most of the time, and has occasional power surges, like ive pressed the gas pedal when i havent. I'm about to replace the fuel pressure regulator, and was planning to test the O2 sensor. What else should i test/check/replace while i'm out there? thanks!