i am just curious as to what causes this? my 98 360 is straight piped and it has this loud cackling sound right after startup for about 20-30 seconds if i really get on it. i like the sound but why would it only do it right after the truck is started? after i floor it once or twice it goes back to the really deep sound which i like but it seems strange that it does this. there is no muffler but stock cat is still on there if that matters. thinking about ditching cat for magnaflow high flow one. thanks.