I agree with Kaos on the type of RTV. I've used clear, black, Ultra Copper, etc, etc, etc. All work fine. (I do use the RED if available as it is slightly higher temp though not by much) I do NOT do the semi tighten thing. I tighten them fully on the first shot. If it's a pitts style then I make absolutely sure to run a support at the opposite end to control vibration which works to loosen or possibly crack the muffler.