I have a stock headpipe and a FMF stainless midpipe. I cannot seem to get a good seal where the two pipes connect. I have tried Ultimate Black silicone and 762 joint compound. The high heat just burns the stuff off. Also the vibreation creates cracks. Neither of these have produced a good seal. I have two questions: 1) Does anyone have a compound they would recommend to get a tight seal. 2) The leak is small. How much of a problem is this?