I did the headswap using new Ford parts, I've put on 500kms and it ran great. Last night I took off my Mac CAI and put the stock intake on minus the snorkle.I had the AIT sensor hanging on the fenderwell and put it in the stock intake. I also have a K&N filter. Well this morning I noticed that there is pinging if I roll on the gas at 100kph. What the heck is wrong???? I'm using 91 octane.