Awesome. I think its finally fixed. Quick Recap.

The car would misfire when you floor it in neutral, sometimes while driving at high rpms or downshifting.

It turned out that there was a cold joint in the odometer circuit board. I saw a writeup on supraforums.com, other people have noticed this also.
Something about the speed signal that runs through it, the soldering point for it goes bad. All I did is dis-assemble the odometer and touch up each soldering point. Has worked fine ever since (which has only been 12 hrs btw).

Hopefully it doesnt come back.

I did also check all connectors, plug gap, air filter cleaning, and etc. in addition but never got better untill I took apart the odometer.

Thanks All