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After discussing my exhaust mod with a few guys,I may have to make some mods to my modified cats. Seems if you just gut them out,you end up with more of a restriction than with the functional convertor. The exhaust gas will expand into the empty chamber,then have to funnel itself down again to exit into the 2 1/4 inch pipe. This is probally more critical at the first pair of cats. Will have to pull it and re engineer.
 

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Probly has something to do with Barillies princpal (spelling sucks) Increase in preasure, decreases velocity, and an increase in velocity decreases preasure. convergant and divergant (again spelling sucks) ducting, makes this happen. Thats what makes a Jet engine run
Did I just come up with that??????
 

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maybe unbolt the cat and weld a section of 2 1/4 pipe in and bolt the cat back around it somehow so it only looks like it is still there and functional.
 

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The navy made me learn that stuff 25 years ago when I became a Jet mech. All that funny stuff is why jet engines suck, bang and then Blow.
 

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Yep, I did the same thing and found out the hard way too. This time I just went with an o/r xpipe. I may take two of the cats off of my h pipe and have them welded into the x just to make it legal.

I would take your stock H pipe (since you have 2) and cut off the big cats leaving the smaller ones by the headers and weld in a straight tube where the cats were. This should give you the sound, power, without loosing torque and be legal. If you need another H pipe, I stepping around one everyday with 300 miles on it.
 

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i highly recommend the latest issue (September)of 5.0 & Super Ford. they give us descriptions/profiles for about 12 different "Cat-Back/After-Cat" systems. some very interesting comments on how the flows or "swirl" of exhaust gases differs in different systems!!!!
 
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