which ia better to control flex fuel and auto adjust timing and boost according too ethnol content and blend?

 

In my opinion that's subjective. Ask the tuner you want to use unless you are tuning it yourself. Heck the stock ECU can do this with the correct patch. That being said I'm running flex fuel on AEM infinity without hiccups. I wouldn't hesitate to use a link ECU if I didn't have my infinity. Another good option is haltech and Syvecs. Again your tuner will recommend what they prefer.

 

ronaldo9 is right, it is highly tuner dependent.
That said, I am running flexfuel on the stock ecu and have been for 4-5+ years without a single issue.

 

i went with infinity hope it was worth the upgrade from a ems v2

 

At the same time, I also hesitate to choose haltech or ling g4. It seems that I should choose haltech more? ? ?

 

All subjective to a tuners opinion. Pick your tuner, and ask him. Reason being- a good tuner can struggle on a system there not well versed on or has tuned with.