well i had a 08 hhr ss manual and had the gm stage 1 on it and had the no boost problem after i told them what to do and they crimped instead..picked up a 08 hhr ss auto for a song n dance 74,000 miles nothing done to it--my winter ride!!! anyway spoke to vince at trifecta and their standard tune gives me more hp than gm.. so in couple days i will know. $200.00 for flash. i think unless you are going to a bigger turbo the gm tune is useless.. gm is basically flashing it.well see soon

 

unless you want to retain the warranty gms1 is useless. you don't need it for big turbo. trifecta and hptuners can control the boost without the 3bar map sensors

 

yes i agree..