Misfires

[bionicbelly]

Ok, so here is the situation.
Car starts to misfire at high RPM/load. Once it starts to misfire, cylinders 5 and 6 die. The car then has NO power, and a runs really rough. I shut the car off, and restart it, and everything smooths out, until I get a good load/lot of revs.
I can clear the codes, and everything is fine, then I rev the car and every single time, I go to redline, it misfires, SES light comes on as the revs drop, and it runs like ass again.

Codes are P0300 (multiple cylinders misfire) , P030x (cylinders 4-6 individually listed)

So far...
I have replaced spark plugs - nothing
Switched coils from 1-3 and 4-6 front bank to rear bank - Still get identical codes, so basically nothing. (I ordered all new coils today anyway)
Fuel pressure seems to be good as read by INPA. Something like 690ish kPa, and steady, no fluctuations.

I changed the Eccentric shaft sensor about 3 months ago.

Am I missing something here? Why in the F*#$ is this happening? I completely missed a TT at gateway, (after driving there) and have one coming up at Mid-O next weekend. I NEED to figure this out.

I do have have the INPA tool from bimmergeeks, but no experience with it. If there is something I should be looking at with it, any advise is appreciated.

[bionicbelly]

Update: I found the problem. I switched all the injectors around, new coils, new plugs, switched O2 sensors around, cam sensors, and it STILL had 4-5-6 misfires. I pulled the manifolds off, and the 4-5-6 catalytic converter was plugged. There are kind of two elements, the chamber has a step in it, and both sections have separate catalysts. On this manifold, the top element melted, and plugged the lower.
I cut windows in both cats, pulled all the substrate out, and my good friend welded them back up, and all is good.

[Tarpon]

Are you tuned or have any modifications that my have caused this?

[bionicbelly]

No tuning, engine is completely stock.

[chris_flies]

Interesting problem...

I've never heard of someone melting their cats, that deserves a

[bionicbelly]

[02Pilot]

Does your engine consume any oil? Cats can clog due to oil burning off on the substrate.

[bionicbelly]

Originally Posted by 02Pilot

Does your engine consume any oil? Cats can clog due to oil burning off on the substrate.

Not a drop. It had a lot of leaks when I got it, but I cleaned everything and put in all new gaskets. (ALL new gaskets.) it only has ~60k on it. It definitely does not burn any. It happened at NCM, and I am pretty sure it was just because I was running it so hard. It is a long fast track, so most of the time it lives between 5k and 7k RPM, and WOT.