since i installed my stacks, i get a vibration like the pip is too tight. so i installed a 18" piece of ss flex pipe just before it goes into the bed. helped some. last night i flipped it and put the flex pipe off the down pipe and solid pipe back to the elbow. its about the same. and had the engineer a temporary holder, because the pipe rested down on the crossover. my question is what do u guys use between the down pipe and the elbow up into the bed. i was thinking about just running a full piece of flex and taking out the solid pipe.