I use to run a similar setup on a H9 edge 540. OS 1.60 fx with perry pump. I used an 18x6 prop and an OS F plug. The F plug helps with the midrange throttling in this engine. I also never used more than 10% nitro. This engine likes lower nitro like 5 or 10 percent. You could try to run it with a regular muffler to see if the tuned pipe is causing the problem. An improperly tuned pipe will also blow glow plugs.