you get to those flex pipe bolts from under the cab , lift and support the boom , raise the cab , soak the bolts with some good quaility penetrating oil , use about 2 foot of extension on your ratchet and you can get to the bolts , these bolts break off frequently from being rusted up in there , take your time , it is pretty hard to try and drill and tap the bolt with the manifold dtill on the engine and taking out the manifold is no picnic especially if it is turbo engine , if you do break one or two off it isn't over yet , sometimes you have enough room to drill thru and put a nut behind the manifold , I have also grinded away one side the nut to get some more room and line up the threads , some manifold you can nut two of the bolts but the other two don't have enough room , there are these little c-clamps they use to hand pipe hangers from the celling , you can use one of those to clamp the spot where the bolt broke and it will hold it all together ..........a trick when going back together is to use some sewing thread and tie 2 corners of the gasket to the flex pipe , this will make lining up the bolts and gasket much easier for you ...................what is hard sometimes is getting the flex pipe out of the muffler if you are saving the muffler , on ones that are really stuck in there I will cut the flex pipe flush with the muffler inlet tube , put a slice in the pipe with a torch and then colaspe the piece of pipe and pull it out with pliers ....................