I have a 2001 32v 5.4 v8 navigator. It rattles or.ticks pretty bad when.it.starts and has a.really bad loose metal noise when.accelerating or at.low.rpm. it.has 230k on.the.engine. my service engine soon light is on.and.i ha e a.code.for p0401. The.noise sounds like its from the front lower block drivwr.side. I cant rwally tell if all the bolts are there in the exhaust manifold. I really need help...this things chugs gas like nothing. 8 mpg. 11mpg on highway. I have yet to do oil change since i bought the car. Spark plugs were replaced but thinking of doing then again to make sure. Any and all help is greatly appreciated.