I've got no experience with this "pre" CAT you're talking about, as mine never had one, but I do know about rusted bolts.
My truck's muffler bolts have all rusted into powder over the years, but now since all my piping/CAT/muffler is new I don't have a problem.
I did, however, have a problem when I removed the header's heat shield bolts. Those were '96 stock, and half the 10mm bolts broke in half. That didn't turn out to be a problem as they broke flush. I got what I wanted.

A 1997???? Are you sure???? The 1997 does NOT have the cat bolted to the exhaust manifold. If you don't believe me go to kiausaparts and look. The 1997 has ONE cat, under the driver. The 2 cats started in 1998 and continued up thru 2002.

When you do your search in kiausaparts the "chassis" section shows the exhaust system. The "engine" section shows the exhaust manifold. You will see the differences. Different part numbers too.

Did you take some picts of your engine bay without the shields?

No, not yet. I'm kind of waiting for the time I get all the pictures I want at the same time, in one big session, but I'll go ahead and get a couple of the engine bay for you in the meantime. Just don't give me the raspberries for it being filthy.

No mike I'm not posotive. Thats what he said though. I asked / told him I believe three diferent times that I needed the preheat cat and one time in an email I even told him it was the one just under the manifold. He said thats the one.

I'll tell ya ..... If I get the other cat .....

Hey just a thought I'm about to get my exhaust done here pretty soon also. I checked on my "96" and there is a warrenty for the cat (8 years or 80k). I'm not sure about the 98 but you may want to check it out.

Thank's, I haven't even checked though. I figure that if there is a warrenty then im out of the picture anyway. I have 116,000 on my 98.

Well, I just got a Magnaflow cat and XL 3 chamber muffler on 2.25" pipe.
Other than the added decibels, I'm not feeling any difference in my ride.
The tech told me any bigger than 2.25" (which he wasn't exactly confortable with in the first place) and I would start losing enough back-pressure to lose torque for high-end horsepower.
I didn't want to lose torque so I agreed to the 2.25" pipe.
I drove it around for about 20 mins and decided that the noise level was far too annoying to keep. I went back and had them install a baffle in front of the muffler to quiet it down. It's still loud but more of a contained annoyence.
I haven't reset the ECU yet, so I'm not sure if I will see any performance gains out of this setup.
Maybe it's there, but I'm sure the gain is small if any.
Any suggestions? The engine still seems to choke at high revs. For example, if I punch the gas at 65mph, the revs float around 6 grand with little increase in forward momentum.

Well, I've decided to take the KIA back to have the muffler replaced. The damn thing sounds like a fart-can, which puts me into a group of drivers I don't wish to be associated with. >_<
You'd think I was breaking the sound barrier with all the noise. And that's what really pisses me off about the thing.
I told the guy a made a bad call and wanted just a standard muffler on there.

Don't give up just yet. At my work a bunch of guys have said the same things about Magnaflow mufflers on their trucks. In fact, my muffler shop friend said he'd never put one on mine. He doesn't like them at all.
Take that as you may, but he tells me there's a lot of differences between mufflers. He should know. His shop here in Vegas is huge.
I humbly recommend you try something like my setup, or at least something near it. If you had EXACTLY what I got I promise you wouldn't change it.
Guys, I'm still trying to get pictures of all my stuff, so be patient. It'll be soon.