So i recently purchased cold air intake and i have problems now

I bought a universal tube with a K&N filter and another smaller filter i forgot what it is called , Anyways i have a 2003 3.8 6cly mustang, the problem i noticed is when i driving and i rev my engine then release the car will rock foward and back real fast it seems more towards the back it rocks, it is a kind of violent rock i dont think its a normal rocking motion because friends have them and they dont have this problem, If u know nething about this please leave some information so i can figure out what the problem is.Also i have the Service engine sign on my dashboard lit up to.