well you don't NEED a highflow cat. you can chop up your old one.
but it's all a fitment thing, I don't know if this header is going to leave space for a cat before our flest pipe. it may just end up flush with our flex, in which case you would have to chop up your cat anf fit it in after the flex.
again this is where I know nothing about exhaust and I don't know if you can legally put a cat behind the flex or if it defeats the purpose of a flex, etc.
but what I'm trying to get accross is that you might not be able to fit a cat before the flexpipe.
our flex pipe is pritty specific it curves all over the place and goes through alot of stuff, so if we can keep it there, thats great news!
Taking a second mental look at our setup it seems like it is going to fit right up to the flex pipe, so it might go somethign like this-
Donor for escort flange- $50-ish
Donor for Focus Flange- $50-ish
which would fit your ideas playa, but heres the problem, with a possible solution!
IF the header leaves no room for the cat before the flex pipe you would have to-
chop off the flex pipe's top flange
put on the donor escort flange
chop off your stock exhaust flange
put it on top of your stock cat
chop off your stock cat before it bends
put on the focus donor flange
then connect the "cat-back"
PROBLEM: cat bacl will be too long because you had to put the cat-converter after the flex pipe
POSSIBLE SOLUTION: get the ZX3 cat back, it's about 6" shorter and might fit perfectly!
I still have a Focus parked, I might fix it up one day.