I recently bought a 3" magnaflow cat back system (stainless mandrel bent) and decided to lose the cat as well. So I bought a few pieces of 2.5" and some clamps to rig up the section of pipe where the old cat was. It was really tough to get the 10-15 degree turn in the cat with limited selection of crappy exhaust pipes from auto value. So I went to a muffler shop in town and he said if I dont have something flexing in there (like the ball joint to the old cat) my welds would break and make for some annoying tick's and rattles. He gave me an old 2.5" flex joint he took off not too long ago and said that would solve the flex issue and make up those few degrees i was trying to turn.

After some patience and wrench throwing I bolted up the new system, (temporarily, I will weld final product) and that darn flex pipe is causing some clearance issues. since the only hangers are on the tail pipes, the pipe from the axle back to the flex joint sags. My question is, do I really need flex in the exhaust system or was I misinformed?

Sorry for long winded story

 

camaros didn't have flex pipes.i have a three inch cat back system with out a flex pipe.

 

Iv done them both ways, I Put the flex at the collector of the Y-Pipe, Right where the channel for the cat starts, Then the cat and they fit fine.
Iv done quite a few where the customers didnt want to spend the extra 100$ for a good flex and never had them come back
Its a good idea if you got power / Headers.

Also there is suppose to be a hangar coming down from the output shaft. The stock one dont fit so good so i normally make one out of a heavy duty southern and wrap it / weld all the way around the pipe. Takes stress off the muffler and headers / manifolds