I got a new catalytic converter, new spark plugs, and *another* reflash with my "engine recall" just recently. Before I had this work done, I noticed there was an ever so slight hesitation after each upshift when accelerating hard. Now it's gone. It also doesn't seem like it is slightly losing steam between 7000 and 7400 rpm like it did (or not as much). :D Does this make sense? Would a bad cat cause the ECM to do something different for the brief moment that I'm off the gas in an upshift or when the intake changes (I forgot what it does at 7500)? I never got any CEL.

I also got the new "northerner" battery and it starts really fast now. I'm pretty happy.

the battery is part of the engine no start TSB, it comes with a faster Starter and plugs as well.

the CAT, they will replace it if they think(or you've complain before) that there is a problem. thats like a thousand bucks worth of stuff right there :D

Recall will put you on the newest flash level.

Give it a few runs for your computer to re-learn.

Yeah I knew that's pretty much what they planned to do (assuming the engine didn't need to be replaced). I was just curious why it would accelerate differently. E.g., when upshifting, does the engine put out foul air (I've heard they do) and the O2 sensor after the cat catches it (because it doesn't get cleaned by a bad cat) and tells the ECM to do something different for a brief second.

The cat will allow the engine to exhale a lot better. I have had 4 replacements to date (33k mi). The coils and plugs will also improve the feel.

no.

probably the change of spark plugs.