My 1987 325e has been running really bad: very poor acceleration, excessive vibration, slightly smoky exhaust, etc. It has brand new platinum plugs and high quality wires. Today I pulled the plugs to see what I might find, and it was not good. Plugs 1,2,3 and 6 looked good, but #5 came out drenched in oil and #4 has traces of oil. What are the best and worst case scenarios?