The car starts fine, drives well for about 2 hrs. In stop and go traffic after driving it for 2 hrs, the RPM starts to sporadically drop from 700 to 500 and eventually dies on me and if it doesn't die, the check engine light turns on and the tcs as well. If i keep driving with the check engine light on, the sporadic drop of rpm continues while I continue to drive and eventually it dies. It will start again but the symptom continues.

The code that comes up is P1300 bank1

I have a 2001 IS300 and here's what I've changed so far:
Spark plugs - Iridium (all)
Ignition coils (all)
ECU
Ignition Module
Harness has been checked for faulty wiring and my mechanic says its good.

I still have the original battery from when I fist bought it (after market) it's probably more than 2 yrs old.
Can anyone please help.

BTW: I am a newbie to this site and a newbie is300 owner.

Thanks
Jay