well my theory about the spark plugs had some interesting results:

I bought some cheap plugs from amazon and threw them in. It started up and run just fine to the barbershop to get my hair cut, but I decided to take it for a quick spin on the freeway... I tried to push it on the onramp but there was a bit of traffic so by the time we were going ~60mph, it wasn't doing anything wrong (i.e. no misfires). I got off at the very next exit then got right back on at the next onramp and this time had some room to rev her up - and boom misfire heaven (or misfire hell?). This time however it didn't stop and it was - for maybe the first time - VERY noticeable. There was a significant drop in power and when I revved it would hardly give me any jump.

I immediately got off the freeway and it continued to misfire and limp along. This is intriguing as it hasn't happened like this before. Usually the misfire is only after pressing the car hard, then goes away after I'm done asking for extra power (on an onramp, passing a car on a two-lane, etc.). I limped home the last 1-2 miles, the CEL blinking the whole way.

Was it the new, cheap plugs? Is whatever happened to it just naturally getting worse and the plugs have nothing to do with it - merely coincidence? No clue. If it IS the plugs, why did they do just fine and low, city speeds when running errands?

 

Have you checked the fuel pump yet? On the other post I mentioned it.....it's pretty much all that's left....bad gas, clogged carbon filter on fuel pump makes some cars misfire etc...you've put in a new fuel filter already.....so when you tromp on it, you are pushing more fuel and that's when the misfires increase....cheap plugs may make your misfire worse because of quality and fuel.....just reminding you....lol

 

Unfortunately all I have on the fuel pump is that the shop said they tested it already. I believe them but really only because I have no reason NOT to believe them.
I think though, if I get annoyed with it again I'll take it to the dealership. Hopefully they'll go through methodically and find some weird thing I didn't notice.
Thanks again!

 

The fpr!

 

Just kidding

Back to its old tricks.

Interesting that that could happen. Change the fpr, NOTHING could make it misfire, and now it's back, a day later and just going around the block.

 

Alright gents I finally got it figure out. Took 2 years

I sorta abandoned this thread for a slightly more populated forum to seek more answers. You can read about my continued distress here:
Random, intermittent misfire (and I've tried everything) - Page 3

Long story short:
It ended up being nothing to do with the engine per se, but rather the power steering pulley. Here's why: The power steering pulley was old and had been removed and replaced so many times it didn't fit correctly and was off balance. It would pull/push on the serp belt which would in turn pull/push on the crankshaft pulley. It was so off balance that it caused the ecu to recognize the pulling/pushing of the crankshaft as misfires.

I owe a huge debt of gratitude to everyone who helped my with this issue along the way. Especially considering I didn't mention anything about the power steering pulley being off balance. It would have been endless attempts to help me which would have continually ended up futile.

 

Glad to hear its all sorted
A while back I had hesitation issues on car and was driving me crazy, over a year of trying this and that, replacing parts only to find out the hose to the turbo from intercooler was loose :/ The relief after the fix never the less is still quite amazing haha.