Sorry Jim, I misinterpreted your previous post. I thought you were saying you used non-resistor plugs.

Since I've never seen a Ryobi, what type of plug seat do they have? Flat, or tapered? My Poulan has a flat plug seat, therefore I use a flat, gasketed plug. If the Ryobi has a flat seat, try using the longer, flat, RCJ7Y plug. It'll increace your compression slightly (very slightly).