all cars run more than one converter
Not entirely true. Depends on the year. Most OBD-II cars probably run two or more on all cars, but pre-OBD-II cars didn't. Dual cats weren't available even as an option on GM's V-8 F-Body cars until, IIRC, 1989 or so, which added an extra 10 horses from being less restrictive (as opposed to their prior design that had them cramming two 2.5" pipes' worth of exhaust through a single 2.5" cat after a Y-pipe connection) - they still combined the two into a Y-pipe and single main intermediate pipe AFTER the cat, but there was only one cat ... pretty lame design for a "performance" vehicle.
Also, a lot of Fords of the pre-OBD-II (pre-'96, mostly, or pre-'94 in a few cases) era had only one cat. Chances are, if it has a Y-pipe exhaust connection (V-6 or V-8 cars), it usually had a single cat ... excluding Fox, Panther, and MN12 platform vehicles.
Later MN12 models had THREE cats - two standard cats, then a single cat that also served as a Y-connection. Weirdness.
I think I even remember seeing a stock H-pipe from a late-model 4.6 (either a Crown Vic or a Mustang) that has SIX catalytic converters on it.
Anyways ... all that aside, most new high-flow cat H- and X-pipes available through the aftermarket only use two cats, and they're more compact than the stock logs. Makes for a lot fewer headaches with fitment and installs ... except in the case of UPR's, because their welders are friggin' idiots that put the cats an inch too far back...
@ "bat in the cave"
