Thats a fuel trim code from DM. The most common problem for that is a a/f meter but, I've seens 02 sensors and egr valves cause that code as well. In actual valves what is the idle reading? It should be in 18 zone and jump into the low to mid 300's at the rev limiter. The o2 is a easy check, whicle looking at o2 actual valves either run the air pump activation or jump the pump while holding the backflow valve open, the o2 should get below 40 mv in 60 seconds or less and hold that, if it falls but wont make it under 40, time for a o2. (however, this is normally accompanied by a secondary air injection code.)
You also might have a bad fuel pressure regulator. Find out where the adaptation is and if its lean limit or rich limit, MAS's tend to be rich limit and regulators tend to be lean limit.
I've not seen a EA cause a 0170.
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