I have an OS Max 61 with a Slimline muffler that is very loud. The muffler offers such little back pressure that I must use a Perry pump on the model. I was under the impression the rule states that my engine must have a muffler. But one member at our club has informed me that my engine is in violation of the sound rules. Our club has no specific sound rule. SO I am assuming that they must mean there is an AMA sound level rule. I do remember a 90db rule years ago, but I cannont find it now. Is there an AMA sound level rule at present other than the requirement to have a muffler?