Could well be if the oil is saturating the spark.
Try cleaning the MAF.
The idle on mine was terrible when I got it. I changed plugs, oil, filters, coolant ,thermostat, temp sensor. Idle was the exact same.
Had a scoot about the forum and cleaned the MAF in some alcohol, used some 10k boost and checked/cleaned all breathers. Cleaned all the electrical plugs I could fine, cleaned throttle body. Also found vac pipes in fpr and dump valve split. After I done all this I disconnect the battery overnight. Reconnected and turned ignition on till the throttle plate setup and all was well. Idle was high and erratic fir about 10 miles. Now smooth and steady all the time.