My 2006 Challenger 215SC has just recently lost about 25% of power and 7-8 mph top end. I had Jerry replace the ceramic washers with metal and it ran fine for 3-4 trips to the lake. The next time (1 day later) there was a noticeable power difference. I checked and removed the air hose on SC and tried spinning the impeller and everything seemed fine. I switched gas and even went to premium after usually running a mix of regular and mid-grade. I haven't checked spark plugs because it's not missing and I've probably only done around 15-20 hours since having a full service. I've checked wear ring, etc. and everything is like new, no damage. Sound is the same except SC is slower to respond after quick turn. Any ideas? Thanks!