hey adam , the dansk headers i got already had holes for the o2 sensors..i had to have the rear o2 moved to the rear of the second set of cats. but i still get a 2096 cel error everytime after about 160 miles. it says there is a delay error on one side of the car so replaced the front sensor and still got the same error.then i switched the 02 sensors from left to right to see if the error moved with the sensors... i got the same cel again 2096