1994 Mercedes Benz E320 rough idle below 900 RPMs

I recently bought this car. It ran horribly. I knew it needed several sensors replaced. So far I replaced MAF sensor, intake air temp sensor, plugs, wires, coils, coil boots. It still has a rough idle. It did get less and less with everything I replaced. One thing I noticed tho. The first set of spark plugs were NGK. Which helped. When I bought the plug wires and coil boots.I ordered Bosch plugs (I read you should use these). After replacing the plugs with the Bosch (which are made in Russia) and the wires, boots. The car did not have the pep. And seems to idle worse.I think I will put the NGK plugs back in tomorrow and see if it helps. Oh, I also replaced the o2 sensor (Bosch) The engine wiring harness was replaced by original owner. And today I rewired the 3 wire harness that goes to the starter, oil pan sensor, and oil pressure sensor (on bottom of oil filter canister). Because the wires were brittle and bare. This didn't seem to help the Idle issue any. But needed to be done. Do you have any thoughts? Once above 900 rpms. The car runs perfect. Thank you for any insight you can give me on this problem.