This is my first post on this site so bear with me. I currently have stock manifold with flowmaster SI/DO super 40 series catback. The piping is currently 2.5" into 3". I have limited money so my plan is to replace only the headers and cats and keep the y-pipe into the flowmaster. This will hopefully increase flow and make it louder. My question is what size pipe should i use from the headers to the y-pipe and will the flowmaster cat-back hinder my flow so much that i will feel no difference at all from the new manifold? Thanks for any info available.

 

Its only worth putting longtube headers in for performance and volume increase, so in the end you may as well buy a longtube catted kit such as Dynatech, or Stainless Works. Headers are not a wallet friendly mod, much like tires.

 

Ya the more I research my hopes just start slipping away. I may end up just replacing the cats to make it louder and wait until I have enough money to completely redo the entire system with true duals.

 

I just put OBX headers on my truck within the last 2 weeks. It doesn't come with cats, but does include a y pipe that mates up to the headers and runs into the factory exhaust. $517 shipped to my house. It's all the other stuff that eats into your wallet. I was $1,500 in the hole by the time everything was completely done.

If you only bought headers, you would have to weld to get it to mate up Bto your stock y pipe, and nobody wants to weld 16 gauge stainless to regular steel of a different thickness