Vibration
 

So I installed berk high flow cats and a Megan racing y pipe. I have no check engine lights and the car seems to run fine. I've noticed that at around 1600 to 1900 rpms there is this vibration and rumbling sound. It's very subtle. I don't seem to notice it in 6th or 7th gear but seems it's at it's worst in first to 3rd gear. More noticeable decelerating but like I said it's subtle. I'm pretty certain the car never did this before installing the cats and y pipe. I don't know what I could of jacked up with the install, it was straight forward besides through everything possible to get the blasted demon bolts out. I was thinking a possible rich or lean mix at those rpms because the car is running fantastic. I don't thinks it's a drone, if it is it's the deepest drone I've ever heard...

I would bet my money, the y-pipe is MM away from cross member brace. I would definitely start there for the noise. What you have to do is loosen everything up, push up on exhaust away from cross member and tighten every thing up while you still pushing up on exhaust. If that does not work you may add spacers to lower the cross member brace just enough to clear the exhaust.

I will give that a check as soon as I have an opportunity. Thanks for the input!