I had the same reaction when using the Hobby Shack brand plugs a long time ago. They would last a flight or two and not give good runs. If you can try the Enya #3 plug. It is not cheap but they do last a long time and will help with a rich running engine. I forgot to metion that I also wrapped the idle needle with teflon tape to help hold the position, mine is a little bit on he loose side.

Dru.