I have an annoying exhaust vibration at around 1200-1400rpm when accelerating slowly [like through a parking lot]. My car came with a Borla cat-back. I know some people have had the same problem with the Borla, but would I need to do to fix the vibration?

 

Do you know where the vibration is located? Is something loose? Something vibrating against your car's body? A bit more description on the vibration would be make it easier to give you a suggestion.

 

The I-pipe on my old Edelbrock catback rubbed on the rearend under light throttle. I did a temporary fix by wrapping the opposing area with some header wrap to act as a cushion. However, as mentioned above, it is all guesswork unless you find out exactly where the vibration is coming from.

 

It's coming somewhere from the rear.

 

Might be worth checking the clearance between the muffler and the fuel tank heat shield. I recently installed a catback and I have a vibration caused by this. The clearance looks to be about 2mm or so but its enough to make a metallic growling sound under light load.

I have not bothered yet to do anything about it but my first idea was to wedge some glass fibre insulation into the gap rather than get under there and loosen everything and move it all about. Thats laziness for you.

 

Check the lateral support that is right above the rear pan hard bar. The Borla y-pipe is real tight there and can rub.

 

I would also check where the I pipe goes over the axle. Make sure there is ample clearance there. If any piping looks close to any of the car's structure, youll get some vibrations under load.

If your exhaust system isnt welded, loosen it, arrange it so that it clears everything... maybe using some pieces of rubber or something as spacers where it looks tight, then tighten it back up. If its welded, you may need an exhaust shop's help.