#1 and #3 spark plug cylinders were leaking oil. Swapped all gaskets per DIY on this site minus moving the air cleaner (thanks). New plugs, oil and filter. Idle is smooth as butter now.
Followed up with new exhaust hangers, primary O2 sensor, gear shift gaskets/seals, transmission output seal and stupid little overpriced light bulb for the HVAC controls. Got the OEM plastic "euro" style 5sp shift knob.
331,200 miles and 33+mpg driving 75mph on highway. 
PS
Engine has consistently seen ONLY Castrol 10W-30 and carbon build up was insignificant. I rarely used Castrol before, but I will never use anything else now.