Still rough idle

Hello hope someone can help me. I have a 1992 cadillac coupe deville that idles extremley rough. It drives ok slight hesitation from a dead stop but other than that its ok. I have replaced distributor cap rotor and coil. New plugs and wires. Fuel injectors have been cleaned.I dont hear any "hissing sounds". I have done a compression check and all eight read between 130 and 150. I am hearing a exhaust rumbling. Can it be possible that the exhaust system is the cause? Any help would be greatly appreciated I am new to this area and have not found a mechanic yet I can trust. Oh yeah no codes just.7.0