More Catalytic Converter Questions

I don't want to belabor the topic, but in dealing with the catalytic converter failure I mentioned in an earlier thread, I just read that using gas with too high an octane rating can also burn a converter
out.
Since I've been using premium (93) in my 380sl, whereas I think MB recommends regular (89) for it, I'm wondering whether this also contributed to my converter problem. OTOH, when I used regular, I got a significant amount of pinging, which went away when I used premium. So I switched to premium some time ago.
As I'm getting ready to replace one or both of the converters on my car, I was hoping someone could tell me whether I should continue using premium, go back to regular, or switch to a mid-grade (91 octane).
I was also wondering whether I should replace the cat on the driver's side with a true cat, a pre-cat, or simply a pipe, considering Tiger's statement that pre-cats aren't needed anymore (other than on the 3-way systems Karl mentioned).
In fact, while researching exhaust systems for the 380sl, I noticed that some have driver's side cat's, some have pre-cats, others seem to have just pipes, and prices differed significantly. For instance, catalyticconverterwarehouse.com has a driver's side cat made by Quali-cat for $67.61 delivered; convertergeek.com has a DEC that seems to have a pre-cat for $93.06; and a whole system for $311. made by Eastern (40061) only has pipes on the driver's side.
I've decided to go with a Magnaflow universal on the passenger's side, and I'd prefer to go with the Quali-cat for 67.61 on the driver's side. But I never heard of Quali-cat, and google didn't turn up anything on the company.
So any advice on the best way to go here would also be greatly appreciated.
Larry
.
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Here in California, before I moved to oregon:), the MB's that had gypo cheapo cats installed with no pre-cats almost always failed the biennial smog check. 9 times out of 10, the NoX was way too high. The other failures were too high HC and CO because the cheapo cat was too small.
<Larry Johnson> wrote in message

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Octane does not damage converters. Tetraethyl lead does/did.
Someone is blowing smoke up your chimney.
The MB cars that are designed to run on premium unleaded use the same cats as the ones designed to run on regular unleaded.
<Larry Johnson> wrote in message

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wrote:

an octane rating could kill a converter specifically by causing carbon deposits to build up in it. See, for instance,
http://theserviceadvisor.com/octane.htm
http://www.convertergeek.com/content.wws?fname=pre-installation-checklist.html
Larry

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By the way, Karl, can you or someone else tell me the best way to loosen the bolts that secure the left cat to the exhaust manifold on my 380sl, so I can replace the cat? That is, should I try to loosen them from the top by inserting a ratchet down through engine compartment, or from the bottom. Or am I better off having a muffler shop do it?
Thanks again,
Larry
wrote:

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Pneumatic impact gun is the only way to remove them... they are rusted and welded in place by the cats.
No... high octane does not kill the cat. Your car only needs regular... 87... that is all I put in my 380SE when I had it.
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wrote:

Thanks. Tiger. I have an electirc impact gun, which should work. But should I attack the bolts from under the car or the nuts from above, and do I need someone or something to hold the otherside while I do.
I've done quite a bit on this and other cars, but never this. SO any advice would be appreciated.

Theoretically, but as I mentioned, I got a lot of pinging with 89 no matter what brand I used, and it went away when I use premiuim. The car seems to have a lot better acceleration with premium, too. Can't say why, though?
Larry
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I would attack from the bottom. If the top spins, put a combination wrench on the top and attack the bottom.
Pneumatic is much more powerful than the electric one... consider investing in one... a small 3 gallon compressor and a impact gun is all you need.
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