1987 Porsche 924S - Replacing Catalytic Converter

[PHOENIX0077]

Hello, all! [cross-posted on Rennlist]

The story: I have a 1987 924S which currently has a straight pipe (welded to the 2-1 exhaust pipe from the manifolds) in place of the factory catalytic converter due to the exhaust failing quite some time ago. I've since moved to a state which requires inspections of smog equipment (MO), so I find myself in need of a new cat so I can actually drive it. Given I can't see into the future, I'd just as soon do it properly as there's a chance I may move to St. Louis or some other place where they actually bother to measure emissions, so while I'm on a budget (yes, that nasty word!), I'd just as soon do it once rather than multiple times.

The problem (other than budget): as you are undoubtedly aware, the part listed for that model/year in the catalogue, #94411198903, is NLA by Porsche. Same for #94411198703 (the 2-1 exhaust pipe leading from the manifolds to the cat). I've found a place that can sell both parts used; I think that is sufficient for the exhaust pipe, but I think a new cat makes more sense.

My question/s:
1. If one looks at the parts listed for the '88 924S, #94411198905 is listed as one of the two possible cats for that model (the other being the same as the '87). That part IS available (for an exurbanite price, as is typical). Is anyone aware of a reason I couldn't use it instead of the "correct" part?

2. I've found part numbers for Japanese/Swiss 944 cats (from the 1989 944 catalogue) - I'm assuming those won't pass a US emissions test, but I'm not familiar enough with international requirements (or what most states use as a baseline), so I can't help but wonder if one would be fine.

3. Does anyone have experience trying to run the MSDS headers and a full exhaust from Lindsey Racing? I'm concerned swapping the headers will be PITA, but the price is tempting (that said, I'm a firm believer in getting what one pays for).

4. As for installation of a factory-type exhaust, the parts diagram has a sleeve installed over the exhaust pipe and cat, but I don't see how it is supposed to be affixed to the parts. Is it supposed to be welded or clamped, or are the parts actually designed to fit together that nicely?

Thank you all for your help. "Worst case" is to simply go to an exhaust shop and have them weld on a third-party cat, but I'd rather stick with the factory stuff if possible.

[djnolan]

According to this Missouri doesn't require testing of cars older than 1995. There is a federal regulation regarding removing emission equipment, however selling or buying such a car is not illegal.

https://www.hagerty.com/media/archived/emissions-and-your-collector-vehicle/

[Monkey Wrench]

Here in BC Canada they had emissions testing but then when most of the old cars became new cars, the testing was removed. for a time the government offered buyouts or things like free bicycles for older cars. many old and repairable cars got crushed, replaced by modern and more proprietary cars with very short lifespans , as intended by manufacturer's designs. Planned obsolescence.

we then had a lot of thefts of catalytic convertors and the new cars stop working and barf up a code . older cars didn't monitor the O2 past the cat. New ones get stuck on proprietary error codes, by intentional design.