It kind of baffles me, I always thought the lower RPM's is better for efficiency......but they engineered this engine to only kick into lean burn >2.6k rpms.
Do you happen to know the specs of the HX injectors?
Are the HX/DX/LX all the same flow rates?
Edit: I may have found the answer here, assuming this information is correct.
http://www.injectorwarehouse.com/inj...linjectors.htm
The reason I was asking is I have a couple sets of LX injectors and was going to send a set out for cleaning if they were the same as HX.