I installed a helix dp and test pipe yesterday. My problem was that the cel fix that came with the test pipe could not clear the floor of the car. I have the Espelier cat back and the o2 bung is more towerds the top of the exhaust, i could not get it on. Does anyone else have this problem? What catback doesn't have this problem?
Now my cel light came on after 1/2 an hour of driving.

 

Is it the heat shield or the floor pan itself?
Sometimes the heat shield can be manipulated if thats whats in the way.

 

If you only need a few MM of extra space, you could mildly dent the floorpan to make room for the O2 fix. Use something soft like a mallet so you don't tear the metal.