My 90 350SDL always seemed slow on acceleration. Rebuilt injectors, new timing chain, set timiming, replaced all filters, checked mass flow pot, water temp sensor, tps, turbo press; all fine. ALDA all the way out. Still poor accel. Went like this for months, then for two weeks ran like a bat out of hell for no reason, geat accel and large cloud of smoke from rich fuel when I jumped on it, still good mpg. Now its back to the way it was. Any ideas welcome