Hi all

As per my earlier post, I've got an Australian 2014 RG Colorado manual with the 2.8Lt Duramax, tuned for towing with max boost/MAP of 300kPa (up from 258kPa max here looking at a stock file)

I'm having a strange lack of power when going to higher altitudes over 500m (1500ft) which first occurred over 2.5 months ago. At first I thought I have a boost leak and have had 2 mechanics look at the car extensively, but car is fine back at sea level and has never logged any trouble codes.

Speaking with the tuner who did the remap, they are adamant it is not related to the tune, but did mention something interesting, that they don't touch the med/high altitude boost maps to prevent turbo overspeed etc.

I'm looking for a 2nd opinion - when others are tuning a Colorado / Duraxmax or other diesel with an E98 ECU, do you change the 'Desired Boost, Med Altitude' map as well as the low altitude base map?

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Comparing the Desired Boost Low/Medium altitude on the stock file appears to target similar boost levels, just the Medium altitude is higher in the rev range around 2400rpm.

Thanks in advance