New a whole new exaust...

I will be buying the flowmaster 40 series muffler and at the same time I would like to buy all new parts from exaust manifold back...So that means the cat, all pipes in front of the cat and all the pipes behind it also. I can find most of the stuff for the cat back...but what about cat and forward?

For a stock Blazer leave the money in your pocket and keep the old y-pipe and cat.  For a new one though if you just must have it, you will need to go to a good exhaust shop that will bend you up a new y-pipe then, just buy an aftermarket high flow cat, and have the exhaust shop put it all together.  Thanks, Korey.