Hi-Flow Cats - Need Advice!

[King Snake]

I have a 2.5" off-road H-pipe laying around and am thinking of purchasing a couple of high flow cats and welding them in this H-pipe to replace my factory 2.25" pipe on my Cobra. Does this sound reasonable? I can get 2 hi-flow cats for around $150. It will be a good bit cheaper than buying a new H-pipe with cats. My biggest concern is placement - I think the converters have to go in between the O2 sensors, is this right? And also, will using only one cat per side set the check engine light? I'm not sure how the EEC uses the signals from the 4 oxygen sensors, maybe someone out there in the know can shed some light on it.

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'97 Cobra, K&N, 3.73s, Rio Red