I have a vicious knocking sound coming from the engine on my pasenger side. It is a 94 6cyl multiport vortek. The only thing that I could have done diffrent then usual is that my son trying to help me out put a can of sea foam in it and a full tank of gas. Since I wasn't aware of this when my blazer got down to half a tank I put a can of sea foam in it and filled it up. Please any ideas I dont want to loose my truck.