It will be ten times easier to replace if you take off the fuel rail. Unscrew the fuel inlet line right next to the rail (prepare for fuel to spill out), then take off the two bolts holding them on. All you have left is to pull... Flip it over and you have the ability to see everything..

I doubt the flame trap being clogged would give you black smoke, but to check for positive crankcase pressure when your engine gets nice and hot pull out dipstick, puffing=clog. You should be getting a slight vacuum there, so no puffing doesn't mean no problem, but ...

Here's volvo's take on your code, what you should take from this is that with excess fuel you're running rich, so you'd be in the lower category. There's eight things that are possible causes, and thats pretty much it. Just go through and when you find out what was wrong you win! Now I might be mistaken, but with the amount of excess fuel you've got i don't think its related to oil, but checking that first knocks out 25% of your options.. You can go to autozone and check fuel pressure on the rail, if you want the guide on that let me know :

DTC information 2–3–1, 2–3–2

Condition

The control module receives information from the HO2S about the fuel/air mixture in the idling and partial load ranges. If the fuel/air mixture deviates from λ=1 the short term fuel trim will compensate this by adjusting the injection timing so that λ=1 is achieved. When the short term fuel trim carries out this adjustment, its mid–point must be adapted by the long term trim. When the long term fuel trim has adapted the short term trim to a maximum value, DTC 2–3–2 (idling range – 0.48 ms to +0.40 ms) or DTC 2–3–1 (partial load range 0.773 to 1.227) and status message Upper Limit (lean fuel/air mixture) or Lower Limit (rich fuel/air mixture) will be set.


Substitute value
None.


Possible source

Upper limit:
-Defective MAF sensor.
-Low fuel pressure.
-Air leakage.
-Faulty sensor signals.

Lower limit:
-Defective MAF sensor.
-Air leakage.
-High fuel pressure.
-Leaking injectors.
-Leaking EVAP system.
-Dirty engine oil.
-Oil level too high.
-Faulty sensor signals.


Fault symptom[s]
-Can result in high fuel consumption.
-Can result in impaired performance.