i had a cat back si/do put on and when i get on it i can hear a ta ta ta ta sound softly....im thinking its my flange donut gasket/s ive looked up under the truck and the pipes are in good shape...im just hoping its not the manifold gasket/s.....anyone have any trouble with leaks in these areas and are the donuts a pain to change??? its an 03 5.4 thanks

and if im planning on cutting the cats it looks a lil difficult to mate a pipe to where i would cut them off...the o2 senors are right before and right after the welds on the coverters and it wouldnt leave any room to clamp anything to how do you guys do this???

 

this is what is probably going on... there is no "donut gasket" like in the old days. this is connection is similar to a flared pipe joint, the pipe is "flared" and mates to the manifold which is kinda' "ball" shaped. the 2 bolts or studs form the manifold use the retainer on the pipe to squeeze this joint tight. take a look at these 2 studs on each side. i bet they have failed, it is a common problem that ford will not address. mine simply rusted in half. if it is not the studs take a look at the rear most cylinder manifold bolts/studs that hold the manifold to the head. they may be broken, or as in my case the manifold may be cracked. you can look closely here while the truck is running and definitely hear a leak. hope you have an extended warranty!!! i am in the middle of fixing mine now, it is a cast iron bitch!!