After replacing fuel injectors (re-manufactured) and a leaking fuel filter, there was no improvement in fuel economy.
It seems the new cam shaft seal installed, is holding up.
Next logical step seems to be, to go back using a cheap full syn oil, due to 'reduced friction' compared to conv-oil.
My main concern is if I go back to conv-oil for a 2nd time, then the fuel economy will be worse now, than it already is. Before I used syn oil for the first time, my mechanic may have used syn-blend.
CEL hasn't come back, but its still too early to tell. If it does come back, ignition coil seems like the next best step, according to google searching.
There has been less to no fumes, and car acceleration doesn't 'noticeably increase acceleration' after 5,000 RPMs, i.e. better acceleration from low RPMs, and less need to downshift.