My PST J600R has been working fine untill the last few flights. It will start just fine but when it is at idol it will pop and sputter. As soon as you bring the RPM's up it goes away. It wont flame out or anything but I dont know why it would be doing this all of a sudden. On another note I noticed that I have an exessive amount of oil residue in my pipe after shutdown. I dont know if the two are related but any help would be grest.

Thanks

P.S I also made sure that I am using exactly one quart of turbine oil to exactly five gallons of fuel