turbo

[NDSNOWPLOW]

Hi to everyone, I'm new to the site and here is my ??

I installed a Hypertech programmer about a month and a half ago. I like and it does well for my purposes. It is set on the max power output which is almost 100 hp gain. I drove the truck on the highway shortly after installing it and drove about 100 miles, my mpg was 20-21, pretty good I thought.

This weekend I drove another 200 miles on the highway both times pulling nothing, just the truck. On the 200 mile trip and -10 to -15 degrees out my mileage went down to 15-16 mpg. and the turbo was boosting at 10 psi all the time. Previously the boost was only running at 3-4.

Does anyone know why my turbo might be boosting at 10 psi with an MT truck on the highway?

Any responses will be a good start...thanks