If I wished to replace this janky high-flow cat, would a downpipe be recommended and then the cat back?

 

The reason I suggest the downpipe is because it eliminates the U-Bend and replaces the cat at the same time. It's also competitively priced when compared to purchasing cat only then having it welded.

Magnaflow Downpipe <- Link

Once you have the part number do a search and you will find it for a lot better price compared to the prices on Magnaflow's web site.

 

Perhaps this will help you:

 

Yeah, that's the same thing I was thinking.

 

Looks kinda like mine under there, but yeah get a down pipe

 

Thanks Mod `Mike & Member's for your posts & help.
It makes me proud to be a member of our Monte Carlo Family..

Mod `Mike, thanks for taking the time to post your pic's of the system. I was searching for those, but couldn't find.
(Pictures are worth a 1K words 4-Sure)
Good Luck `Tyler on your repairs & not gett'in codes

 

Ugh, why on earth did they leave the ubend

 

Good Morning `John,
The only reason I can come up with is that they were on drugs, or they did it that way to slow the Monte down ,because the Monte was just 2 fast (Lol) What ? ~> lol

Or maybe the GM designer of that monstrosity U-bend did it because he owns a aftermarket exhaust company with replacement downpipes etc. to sell everyone... LOL

 

Downpipe and cat-back it is! Weeeeeeeeeee spending money to correct over people's stupidity is fun!