Engine Misses when Hot. Need help.

[SA]

I need your help.

For the past few weeks my car has been missing. This only occurs when the car is warm-hot (~190-200 deg) and the engine only misses on the driver side bank (cylinder balance test verified).

This is how it starts-
I start the car in the morning. All is well. I drive to my destination (~15miles) and all is still good. Temp is about 180.
I shut the car off and restart it a few hours later and take off. I hit traffic and the temp rises to around 195, I turn my fan on and the temp drops to 180 or below. If I drive for, say, an hour like this (hot, cool, hot, etc, etc), the car starts to miss. All of a sudden –like at a stop light.
I drive it home, where I leave it to cool for a few hours. Once it's stone cold, I start it up and no problems.

This has never happened to me before. It all started when I re-did my heads (FYI -not my first time doing this). I don't think that it's anything small like a vacuum leak or a bad wire(s) or cap because it ONLY happened when it gets into closed loop (or open loop –I forget. Whichever "loop" occurs once the car is warm).

As I stated above, I have verified that the driver side bank is the one that is missing and it spits out a lean code, BUT again it only misses when it's hot (I've done the test when the engine is cool and no codes)

I remember using a magnet to pick up a bolt that fell in my driver's side h-pipe pipe. It wasn't too strong, but maybe that screwed up that side's oxygen sensor? Would a bad oxygen sensor cause a miss like this? Any way to verify?

Could bad lifters cause this? I have a "new" tick coming from the top end that I didn't have before. It's not the regular "sowing machine" sound. More like two spoons hitting each other. It starts around 2000rpm and progresses from there. I thought it was the injectors, so I bought some new ones (I needed the upgrade anyhow). I replaced the injectors today and still no luck. Mind you, power is great when it's cold -it pulls to the moon and back. :-)

I'm stumped. The thing that really throws me off is that is only happens when the car is hot.
I bought some new spark plugs today and will be installing them tomorrow (which I doubt will help). My guess it that it's something electrical.

O, almost forgot, could a bad coil do this? I would imagine that it would always miss (hot or cold) if I had a bad coil. I also have a MSD 6AL and a Vortech BTM (blower is not on though). I'll try bypassing these to see if these are the cause.

What do you think it is???