Everything I have read about the evoporative system and the EGR is to help out with emmissions and fuel economy... it sounds like the CEL was on because of your EGR not working correctly (blown gasket)....If you were running rich...my guess would be because of the boost leak...remember, if you are losing metered air the stoichiometric mix is thrown out of wack-rich-plug fouling..
Basically the engineers that design these systems know what they are doing...for the most part
... and have these systems there for a reason whether it is for emmissions or fuel economy...
On the side.... I didn't know you could soak the K&N filters.... I thought you were supposed to spray them with the cleaning fluid, let sit, the rinse from the inside out flushing all the crap out... I guess, if it works, it works....