...rule of thumb for idle adjustment(s) screws is usually: turn screw full in, then counter-clockwise 2 1/2 turns and you should be close...adjust from there...ALSO...if you have a water/filter seperator, change it out and check the old one for water...todays gas is causing water and fuel line degradation problems...did you check the "junk" in the old filter.?.."rubbery type" residues means gas lines need updating for the fuels today...if ok...LP's advise on fuel pressure is right on...BUT...I have had a coil "go Bad" on the high rpm side and the motor did exactly what yours is/was doing...good luck matey.!..
...