I was told to cut out a section of my downpipe and weld in a flex pipe to to eliminate the risk of making cracks in my manifold. Does this sound right? It seems like it would put less stress on the manifold...but do those thing last at all?? Is this something I should do?

 

wen i had my custom downpipe put on they put a 6 inch flexipipe in for that exact reason, and also they also said it would relieve stress on all the joints, and this would reduce the risk of leakage.

 

So what part of the downpipe is the flex pipe welded at?

 

right before/after the cat. If you do it after the cat, you should probably shorten your dp by the length of your flex pipe so it still ends at the right place. That way you can still bolt-on cat-back exaust later if you want. Placing the cat before the flexpipe might marginally help emissions when cold (being closer to the engine means it'll light off faster).