Power loss on the interstate (long drive)
 

I had posted something else about this issue, but it was more of a "give me quick answers" thread. I wanted to post something with more detail, and some other updates I should definitely mention. So back in the middle of April, I drove my 8 down to Mississippi from Tennessee. For the first hour it was running fine, but I got off the interstate in Decatur, AL and noticed a definite power loss. It was extreme enough to notice right away and instantly concern me. I eventually made it to Mississippi by going slow and barely being able to climb hills. The rest of the story goes: I towed it back to Nashville and let it sit for awhile while I tried to get in touch with Kevin at Rotary Resurrection (I had already known I had low compression and was on borrowed time so I finally had enough to afford a rebuild and thought it was an appropriate time).

In the meantime, after a week or so of it just sitting in my garage, I took it Mazda for a compression test as well as a full inspection. The same problem started happening on the way home from Mazda, after it had been running for awhile. Indeed the compression was in the mid 4's at 250rpm, and also I was told my spark plugs were fouled (which is weird because they were just replaced six months ago), and that my catalytic converter was clogged. The clogged cat explained my issues but the part that throws me off is that Kevin took a look at my cat for me and said that he doesn't see any clogging. Let me also mention that he said he was looking at it from the front (towards the headers) and that most cat clogging will begin at the front, not at the back, and that he didn't see any. There are pictures of it below.

http://www.rotaryresurrection.com/bu...s/DSCF3468.JPG
http://www.rotaryresurrection.com/bu...s/DSCF3469.JPG
http://www.rotaryresurrection.com/bu...s/DSCF3470.JPG

If Mazda says it is clogged, but Kevin says he doesn't see any, what do I do?
Could that explain my power loss? Or in doing an engine rebuild, will it solve itself?

I guess my main concern to cover everything I've just said is that, I'm not certain that this rebuilt engine is going to fix my problem that I had on the interstate that one day, and the day I took it to Mazda. I know it definitely had to be done, but I am concerned that I will get it back and I will still be experiencing the original issue. Any ideas?

The only way to be sure it's not clogged would be to take the cat completely off & shine a light through it.
I've seen pics of cats where it appears to be OK but is clogged.
In my case the whole front half was gone so it was a no-brainer.