xxaarraa

Hey guys,

2014 A6 Z51 with NPP. Installed the borla x-pipe today and everything went well. Except now I have a rattle / grinding type noise at about 1500 rpms in Touring mode - coming from the far rear of the car. Comes and goes, but pretty easy to reproduce at around 1500 rpms.

Could it be that the driveshaft makes contact with the new x-pipe or tunnel plate when I reinstalled them? Is that likely? I reused the stock rubber isolator and mounting bracket in the back like the instructions said to.

Could it be the NPP valves are somehow sticking with the freer flowing borla x-pipe now installed? I googled and saw a thread about hitting the valves with WD-40, not sure if that's related to my issue.

Anyone got any ideas?

MerakiAutoworks

Is it he AFM valves opening and closing?

Try driving in eco mode and see if its the sound. Then sport, should go away.

-Josh

Max Bet

When tightening the bolts at the front end of the x-pipe, the instructions mention tightening evenly so it doesn't pull the x-pipe towards one side. I checked for clearance when I installed mine and it would be easy for it to make contact in the rear if you're not careful given the length of the pipe. I would get underneath and shake your mufflers a bit to see if the pipe hits or rubs anything.

Jack Be Quick Racing

If all you did is swap out the x-pipe, the AFM and NPP valves shouldnt even 'known' the difference. My money is on a clearance issue either at the x-pipe or created further downstream when bolting it up.

xxaarraa

OK guys here's an update. I took it to a muffler shop and they put it up on the lift. Within 10 seconds, they noticed one of the clamps between the x-pipe and stock muffler was tucked way up and making contact with a heat shield. They re-adjusted it, and I drove it back home and did not notice the noise.

I will give it a few days more driving to be absolutely sure, but hoping this is a simple and happy ending.